Immunology: Type IV Hypersensitivity

Questions and Answers

What type of hypersensitivity is caused by CD4+ T cells reacting to an allergen?

Type III

Type IV (correct)

Type II

Type I

Which type of T cells induces chronic inflammation in response to an allergen?

B cells

Mast cells

CD4+ T cells (correct)

CD8+ T cells

What is the result of cross-linking of IgE on the surface of mast cells?

Degranulation of mast cells (correct)

Production of antibodies

Activation of T cells

Release of cytokines

Which cell type is responsible for presenting allergens to CD4+ T cells?

Dendritic cells Signup and view all the answers

What is the primary function of CD8+ T cells in response to an allergen?

Destruction of infected cells Signup and view all the answers

What is the consequence of the release of mediators from mast cells?

Increased vascular permeability Signup and view all the answers

Which of the following is not a characteristic of an immediate allergic reaction?

Delayed onset Signup and view all the answers

What is the primary role of eosinophils in allergic reactions?

Release of granule proteins Signup and view all the answers

Which of the following is NOT a possible outcome of an immediate hypersensitivity reaction in the context of the provided information?

Activation of the complement system Signup and view all the answers

Which of the following mediators is NOT explicitly mentioned as playing a role in the immediate hypersensitivity response described?

TNF-alpha Signup and view all the answers

Based on the information provided, which of the following is a potential reason why some individuals experience severe reactions to allergens while others do not?

All of the above Signup and view all the answers

The passage suggests that immediate hypersensitivity reactions can cause upper airway obstruction. What is the most likely mechanism by which this occurs?

Both b and c Signup and view all the answers

The passage mentions that immediate hypersensitivity reactions can be exacerbated by certain mediators. Which of the following is NOT one of these mediators?

IgG Signup and view all the answers

What is the potential consequence of a systemic immediate hypersensitivity reaction, as described in the passage?

Anaphylaxis with a rapid drop in blood pressure Signup and view all the answers

Which of the following best describes the role of mast cells in immediate hypersensitivity reactions?

Mast cells release histamine and other mediators upon activation by IgE Signup and view all the answers

According to the passage, what is a possible reason why some individuals may develop harmful reactions to allergens while others do not?

All of the above Signup and view all the answers

What is typically unimpressive in Type I hypersensitivity reactions?

Congestion Signup and view all the answers

Which substance is primarily stored in mast cell granules and rapidly released upon degranulation?

Histamine Signup and view all the answers

What physiological change does histamine cause in Type I hypersensitivity?

Rapid vasodilation Signup and view all the answers

In the context of asthma, which condition may occur due to significant bronchial changes?

Bronchial gland hyperplasia Signup and view all the answers

What causes smooth muscle contraction in Type I hypersensitivity reactions?

Histamine release Signup and view all the answers

What type of inflammation is associated with eosinophil infiltration in bronchial walls?

Eosinophilic inflammation Signup and view all the answers

What is a consequence of increased vascular permeability during Type I hypersensitivity reactions?

Fluid leakage into tissues Signup and view all the answers

Which immune cells are primarily involved in mediating Type I hypersensitivity reactions?

Mast cells Signup and view all the answers

What describes the timing of the immediate hypersensitivity reaction after allergen exposure in a sensitized individual?

It develops within minutes after challenge. Signup and view all the answers

Which morphological feature is NOT associated with the immediate reaction to an allergen?

Inflammatory infiltrate rich in eosinophils Signup and view all the answers

What characterizes the late-phase reaction in immediate hypersensitivity?

Inflammatory infiltrate rich in eosinophils, neutrophils, and T cells. Signup and view all the answers

How long after allergen exposure does the late-phase reaction typically develop?

2 to 24 hours later. Signup and view all the answers

Which of the following is NOT a characteristic of the immediate reaction in immediate hypersensitivity?

Delayed influx of eosinophils Signup and view all the answers

Which of the following mediators is primarily involved in the late-phase reaction of immediate hypersensitivity?

Cytokines and chemokines Signup and view all the answers

Which of the following statements about immediate hypersensitivity is accurate?

The immediate response is characterized by a quick vascular reaction. Signup and view all the answers

What type of immune cells are predominant in the late-phase reaction of immediate hypersensitivity?

Eosinophils and neutrophils Signup and view all the answers

Which type of hypersensitivity is primarily responsible for the immediate symptoms of an allergic reaction, such as anaphylaxis?

Type I hypersensitivity Signup and view all the answers

Which of the following is NOT a characteristic of Type I hypersensitivity?

Characterized by delayed-onset symptoms Signup and view all the answers

Which of the following is a potential consequence of Type I hypersensitivity?

Anaphylaxis Signup and view all the answers

What is the primary function of IgE in Type I hypersensitivity?

To bind to mast cells and initiate degranulation Signup and view all the answers

What is the role of dendritic cells in the development of Type I hypersensitivity?

They present allergens to T helper cells Signup and view all the answers

What is the role of Th2 cells in Type I hypersensitivity?

They produce cytokines that promote IgE production Signup and view all the answers

Which of the following mediators released from mast cells contributes to the symptoms of airway obstruction in allergic reactions like asthma?

All of the above Signup and view all the answers

What is the primary mechanism by which mast cells release histamine and other mediators?

Exocytosis of granules Signup and view all the answers

Which of the following is a characteristic of non-atopic allergy?

Triggered by non-immune stimuli Signup and view all the answers

Which of the following is an example of an antibody-mediated (Type II) hypersensitivity disorder?

Myasthenia gravis Signup and view all the answers

Antibody-mediated (type II) hypersensitivity is caused by IgE antibodies.

False Signup and view all the answers

Mast cells are primarily involved in mediating type III hypersensitivity reactions.

False Signup and view all the answers

Immune complex-mediated (type III) hypersensitivity is caused by an overactive immune response.

True Signup and view all the answers

Activation of mast cells leads to the release of anti-inflammatory mediators.

False Signup and view all the answers

Type I hypersensitivity reactions typically occur within hours of allergen exposure.

False Signup and view all the answers

The primary role of eosinophils is to present antigens to T cells.

False Signup and view all the answers

Immediate hypersensitivity reactions are primarily caused by CD8+ T cells.

False Signup and view all the answers

Immune complex-mediated (type III) hypersensitivity reactions are typically localized to the site of allergen exposure.

False Signup and view all the answers

The release of mediators from mast cells is a characteristic of chronic inflammation.

False Signup and view all the answers

Antibody-mediated (type II) hypersensitivity reactions involve the activation of T cells.

False Signup and view all the answers

Eosinophils are responsible for presenting allergens to CD4+ T cells.

False Signup and view all the answers

Immediate hypersensitivity reactions can cause upper airway obstruction due to the release of histamine.

True Signup and view all the answers

Systemic immediate hypersensitivity reactions can be life-threatening.

True Signup and view all the answers

Mast cells are primarily involved in mediating Type IV hypersensitivity reactions.

False Signup and view all the answers

The late-phase reaction in immediate hypersensitivity typically develops within minutes after allergen exposure.

False Signup and view all the answers

IgE antibodies are primarily involved in mediating Type II hypersensitivity reactions.

False Signup and view all the answers

Opsonization and phagocytosis are two separate pathways that do not involve each other.

False Signup and view all the answers

Complement activation is involved in both antibody-mediated and immune complex-mediated hypersensitivity reactions.

True Signup and view all the answers

Antibody-mediated cellular dysfunction is only caused by IgG antibodies.

False Signup and view all the answers

The Fc receptor is involved in the activation of phagocytosis.

True Signup and view all the answers

Neutrophils and eosinophils are not involved in immediate hypersensitivity reactions.

False Signup and view all the answers

The TSH receptor is involved in Graves' disease, an autoimmune disorder.

True Signup and view all the answers

Inflammation is not a part of the immune complex-mediated hypersensitivity reaction.

False Signup and view all the answers

C3b is a protein involved in the activation of phagocytosis.

True Signup and view all the answers

Antibody-mediated hypersensitivity reactions only involve IgE antibodies.

False Signup and view all the answers

The introduction of an allergen triggers the immediate release of histamine from mast cells, leading to the characteristic symptoms of an immediate hypersensitivity reaction.

True Signup and view all the answers

The immediate hypersensitivity reaction is characterized by a delayed response to allergen exposure.

False Signup and view all the answers

The complement system, primarily activated by immunoglobulin E (IgE), plays a crucial role in initiating and amplifying the immediate hypersensitivity response.

False Signup and view all the answers

The binding of IgE to Fc receptors on mast cells is a crucial step in the sensitization phase of an immediate hypersensitivity reaction, setting the stage for a rapid response upon subsequent exposure to the allergen.

True Signup and view all the answers

The release of leukotrienes from mast cells, particularly leukotriene D4, contributes to the late-phase reaction in immediate hypersensitivity, leading to prolonged inflammation and tissue damage.

True Signup and view all the answers

The immediate hypersensitivity reaction is a complex process involving the interplay of various immune cells, including Th2 cells, mast cells, and eosinophils, with each contributing to different aspects of the reaction.

True Signup and view all the answers

The immediate hypersensitivity reaction is primarily mediated by the activation of CD8+ T cells, which directly target and destroy allergen-presenting cells, leading to the immediate symptoms of allergy.

False Signup and view all the answers

CD4+ T cells, upon activation by an allergen, directly trigger the release of histamine from mast cells.

False Signup and view all the answers

The late-phase reaction in Type I hypersensitivity is characterized by the recruitment of eosinophils, which are not involved in the immediate reaction.

True Signup and view all the answers

While CD4+ T cells play a critical role in the development of Type I hypersensitivity, CD8+ T cells are not involved in this process.

False Signup and view all the answers

The term "Type IV hypersensitivity" refers to the delayed-type hypersensitivity reactions mediated by CD4+ T cells and macrophages, and is distinct from Type I hypersensitivity, which is IgE-mediated.

True Signup and view all the answers

The immediate reaction in Type I hypersensitivity involves the release of mediators from mast cells, such as histamine and leukotrienes, leading to the classic symptoms of allergic reactions, including vasodilation, bronchospasm, and increased vascular permeability.

True Signup and view all the answers

The primary role of IgE in Type I hypersensitivity is to bind to Fc receptors on mast cells, facilitating the cross-linking of IgE molecules and the subsequent degranulation of mast cells, leading to the release of inflammatory mediators.

True Signup and view all the answers

Eosinophils, while present in the late-phase reaction, do not play a significant role in the immediate reaction to allergens in Type I hypersensitivity.

True Signup and view all the answers

While CD4+ T cells are primarily involved in the activation of B cells to produce IgE antibodies, CD8+ T cells do not play a significant role in the development of Type I hypersensitivity reactions.

False Signup and view all the answers

What is the primary mechanism by which IgE binds to mast cells, leading to the release of mediators?

IgE binds to FcεRI receptors on mast cells. Signup and view all the answers

What is the mechanism by which CD4+ T cells recognize and respond to allergens, leading to chronic inflammation?

CD4+ T cells recognize and respond to allergens by binding to IgE on the surface of mast cells, leading to cross-linking and activation of mast cells, which then release mediators that induce chronic inflammation. Signup and view all the answers

What is the role of Th2 cells in the development of immediate hypersensitivity reactions?

Th2 cells stimulate the production of IgE antibodies, which bind to mast cells. Signup and view all the answers

What is the consequence of the activation of the complement system in immediate hypersensitivity reactions?

The activation of the complement system leads to inflammation and tissue injury. Signup and view all the answers

How do eosinophils contribute to the pathogenesis of allergic reactions, and what is the significance of their presence in bronchial walls?

Eosinophils contribute to the pathogenesis of allergic reactions by releasing granule proteins that damage tissues and exacerbate inflammation. Their presence in bronchial walls is a hallmark of allergic reactions and contributes to the development of airway obstruction. Signup and view all the answers

What is the role of Fc receptors on CD8+ T cells in the development of immediate hypersensitivity reactions?

Fc receptors on CD8+ T cells recognize and bind to IgE, allowing CD8+ T cells to recognize and respond to allergens, leading to the release of cytotoxic granules and cell death. Signup and view all the answers

What is the primary function of mast cells in immediate hypersensitivity reactions?

Mast cells release histamine and other mediators, leading to allergic symptoms. Signup and view all the answers

What is the role of eosinophils in immediate hypersensitivity reactions?

Eosinophils play a role in the late-phase reaction, contributing to chronic inflammation. Signup and view all the answers

What are the key differences between the immediate and late-phase reactions in immediate hypersensitivity, and what are the underlying mechanisms?

The immediate phase reaction is characterized by the rapid release of mediators from mast cells, leading to symptoms such as edema and vasodilation. The late-phase reaction, which develops hours after allergen exposure, is characterized by the infiltration of eosinophils and the release of pro-inflammatory cytokines, leading to chronic inflammation. Signup and view all the answers

How do mast cells contribute to the development of chronic inflammation in response to allergens?

Mast cells contribute to the development of chronic inflammation by releasing mediators that attract and activate immune cells, such as eosinophils and T cells, leading to the production of pro-inflammatory cytokines and the perpetuation of inflammation. Signup and view all the answers

What is the primary difference between immediate and delayed hypersensitivity reactions?

Immediate hypersensitivity reactions are mediated by IgE and mast cells, while delayed hypersensitivity reactions are mediated by T cells and macrophages. Signup and view all the answers

What is the role of IgE in the development of immediate hypersensitivity reactions, and how does it interact with allergens?

IgE plays a crucial role in the development of immediate hypersensitivity reactions by binding to allergens and facilitating the activation of mast cells and basophils, leading to the release of mediators and the development of allergic symptoms. Signup and view all the answers

How do CD4+ T cells and eosinophils interact in the development of chronic inflammation in response to allergens?

CD4+ T cells and eosinophils interact in the development of chronic inflammation by CD4+ T cells recognizing and responding to allergens, leading to the activation of eosinophils, which then release granule proteins that exacerbate inflammation. Signup and view all the answers

What are the key differences between Type I and Type IV hypersensitivity reactions, and what are the underlying mechanisms?

Type I hypersensitivity reactions are characterized by the rapid release of mediators from mast cells and basophils in response to allergens, leading to immediate symptoms. Type IV hypersensitivity reactions, on the other hand, are characterized by the activation of T cells and the release of cytokines, leading to delayed symptoms. Signup and view all the answers

What role do antibodies play in phagocytosis regarding hypersensitivity?

Antibodies opsonize circulating cells, enhancing their targeting for phagocytosis. Signup and view all the answers

How can repeated exposure to an allergen affect hypersensitivity responses?

Repeated exposure can lead to heightened sensitivity and an exaggerated immune response. Signup and view all the answers

What is the significance of complement-mediated destruction in hypersensitivity?

Complement-mediated destruction effectively helps eliminate pathogens through cell lysis and inflammation. Signup and view all the answers

Why is hypersensitivity considered a form of exaggerated immune response?

Hypersensitivity involves an overreaction to harmless substances, leading to tissue damage. Signup and view all the answers

What cellular components are involved in targeting allergens during hypersensitivity?

Circulating immune cells, such as red blood cells and platelets, are targeted in the allergic response. Signup and view all the answers

How does inflammation relate to the mechanisms of hypersensitivity?

Inflammation results from the immune system's response to allergens, causing various symptoms. Signup and view all the answers

What is the connection between sensitization to allergens and hypersensitivity reactions?

Sensitization primes the immune system, making it more likely to react strongly upon re-exposure. Signup and view all the answers

In what way does the immune response to allergens shift with subsequent exposures?

The immune response can shift to become increasingly robust and potentially harmful with repeated exposures. Signup and view all the answers

Explain the mechanism by which IgE binding to mast cells initiates an immediate hypersensitivity reaction, highlighting the key role of FcεRI and the subsequent events leading to mediator release.

IgE binds to the high-affinity IgE receptor (FcεRI) on the surface of mast cells. When a multivalent allergen binds to the IgE molecules attached to FcεRI, it cross-links the receptors, triggering mast cell degranulation. This release of pre-formed mediators like histamine, leukotrienes, and prostaglandins, along with newly synthesized cytokines, is responsible for the immediate symptoms of an allergic reaction. Signup and view all the answers

Describe the various ways in which allergens can enter the body and initiate an immune response, providing specific examples for each pathway.

Allergens can enter the body through various routes: inhalation (e.g., pollen, dust mites), ingestion (e.g., peanuts, shellfish), injection (e.g., bee venom), or skin contact (e.g., latex, poison ivy). These allergens can be normal molecules, components of microorganisms, or exogenous substances like drugs or their metabolites. In some cases, antibodies to microbial or other antigens can cross-react with allergens, leading to sensitization. Signup and view all the answers

Explain the concept of cross-reactivity in allergic reactions, providing an example of how it can contribute to the development of an allergic response.

Cross-reactivity occurs when antibodies or T cells specific for one allergen can also recognize and react with a different, structurally similar allergen. This can lead to sensitization to multiple allergens, even if exposure to a particular allergen has been limited. For example, someone with a peanut allergy may also react to other legumes like soybeans or lentils due to cross-reactivity between the allergens present in these foods. Signup and view all the answers

Discuss the role of eosinophils in the late-phase reaction of immediate hypersensitivity, highlighting their contribution to the development of chronic inflammation.

Eosinophils are recruited to the site of inflammation during the late-phase reaction of immediate hypersensitivity. They release a variety of mediators, including enzymes, cytokines, and chemokines, that contribute to tissue damage, remodeling, and chronic inflammation. This process can contribute to persistent symptoms and the development of chronic allergic conditions like asthma. Signup and view all the answers

Explain the potential consequences of an immediate hypersensitivity reaction, emphasizing the different clinical manifestations and the factors that can influence the severity of the response.

Immediate hypersensitivity reactions can range from mild symptoms like sneezing, itching, and runny nose to severe reactions like anaphylaxis, characterized by life-threatening airway obstruction, hypotension, and shock. The severity of the response depends on factors such as the amount of allergen exposure, the individual's sensitivity, and the location of the allergic reaction. Systemic reactions involving multiple organ systems pose the greatest risk. Signup and view all the answers

Compare and contrast the immediate and late-phase reactions in immediate hypersensitivity, highlighting the key mediators involved and the time frame for each phase.

The immediate reaction occurs within minutes of allergen exposure and is characterized by the rapid release of pre-formed mediators from mast cells, such as histamine, leukotrienes, and prostaglandins. The late-phase reaction occurs several hours later and involves the recruitment of inflammatory cells, including eosinophils and T cells, along with the release of cytokines and chemokines. While both phases contribute to the overall allergic response, the immediate reaction is typically responsible for the acute symptoms, while the late-phase reaction contributes to the development of chronic inflammation. Signup and view all the answers

Explain how the concept of 'atopic' allergy differs from non-atopic allergy, providing specific examples of each.

Atopic allergy is characterized by a genetic predisposition to develop IgE-mediated allergic reactions, often involving multiple allergens and a history of eczema, asthma, or hay fever. Non-atopic allergy, in contrast, is not associated with a familial history of allergies and typically involves a single allergen, often triggered by specific environmental exposures. Examples of atopic allergies include pollen allergies, food allergies, and pet allergies. Non-atopic allergies can include reactions to latex, certain medications, or industrial chemicals. Signup and view all the answers

Discuss the role of CD4+ T cells in the development and persistence of allergic reactions, explaining how they contribute to the recruitment of eosinophils and the development of chronic inflammation.

CD4+ T cells play a critical role in the development and persistence of allergic reactions. Following allergen presentation by antigen-presenting cells (APCs), they differentiate into Th2 cells. Th2 cells release cytokines like IL-4, IL-5, and IL-13, which promote IgE production by B cells, eosinophil differentiation and recruitment, and tissue remodeling. This cascade of events contributes to the development of chronic inflammation and the persistent symptoms of allergic conditions. Signup and view all the answers

Explain how the deposition of antigen-antibody complexes in blood vessels can lead to inflammation in Type III hypersensitivity.

In Type III hypersensitivity, antigen-antibody complexes form in the circulation. These complexes can then deposit in blood vessel walls, triggering complement activation. This leads to the release of inflammatory mediators, such as anaphylatoxins (C3a and C5a) and chemotactic factors, which attract neutrophils and other inflammatory cells. These cells release additional inflammatory mediators, resulting in tissue damage and inflammation. Signup and view all the answers

Describe the role of cytokines in the development of tissue injury in delayed-type hypersensitivity (Type IV).

In delayed-type hypersensitivity (Type IV), CD4+ T cells release cytokines, primarily TNF-α, IFN-γ, and IL-2. These cytokines contribute to tissue injury by recruiting and activating macrophages, which release destructive enzymes and reactive oxygen species. They also promote the expression of adhesion molecules on vascular endothelium, facilitating further leukocyte infiltration and amplification of the inflammatory response. Signup and view all the answers

Explain the mechanism by which CD8+ T cells contribute to tissue injury in Type IV hypersensitivity.

CD8+ T cells, also known as cytotoxic T lymphocytes, are directly involved in tissue injury in Type IV hypersensitivity. They recognize and kill cells displaying specific antigens on their surface. This process is mediated by the release of cytotoxic substances, such as perforin and granzyme, which induce apoptosis in the target cell. This cytotoxic activity can contribute to the development of tissue damage and inflammation characteristic of Type IV hypersensitivity. Signup and view all the answers

How does the dysregulation of the immune response in Type IV hypersensitivity differ from the mechanism underlying Type III hypersensitivity?

Type IV hypersensitivity, unlike Type III, is a T cell-mediated response. It involves the sensitization of T cells to specific antigens. The primary mechanism of tissue injury in Type IV is cell-mediated cytotoxicity, primarily by CD8+ T cells, and cytokine-mediated inflammation, driven by CD4+ T cells. Type III hypersensitivity, in contrast, is antibody-mediated, relying on the formation of antigen-antibody complexes that trigger complement activation and subsequent inflammation. The immune dysregulation in Type IV involves the inappropriate activation of T cells against self-antigens or foreign antigens, leading to direct cell killing and cytokine-mediated inflammation, whereas in Type III, the immune dysregulation is related to the overproduction of antibodies and the formation of immune complexes. Signup and view all the answers

How can the deposition of antigen-antibody complexes in blood vessels contribute to the development of autoimmune diseases? Provide a specific example.

The deposition of antigen-antibody complexes in blood vessels, a hallmark of Type III hypersensitivity, can contribute to the development of autoimmune diseases by triggering chronic inflammation and tissue damage. These complexes activate the complement system, leading to the release of inflammatory mediators that attract immune cells, such as neutrophils, to the site of deposition. These cells can then release destructive enzymes and reactive oxygen species, damaging surrounding tissues. For instance, in systemic lupus erythematosus (SLE), a chronic autoimmune disease, autoantibodies form against nuclear antigens. These immune complexes deposit in various tissues, including the kidneys, joints, and skin, causing inflammation and tissue damage, leading to the characteristic symptoms of the disease. Signup and view all the answers

Explain the key differences between the mechanisms of tissue injury in Type IV hypersensitivity and those involved in Type I hypersensitivity reactions.

Type IV hypersensitivity is a T cell-mediated response, characterized by delayed-type hypersensitivity. It involves direct cell cytotoxicity by CD8+ T cells and cytokine-mediated inflammation by CD4+ T cells. Type I hypersensitivity, on the other hand, is an immediate hypersensitivity reaction mediated by IgE antibodies. It involves the cross-linking of IgE on mast cells, leading to the release of pre-formed mediators, such as histamine, and the subsequent recruitment of other inflammatory cells. While Type IV involves direct T cell-mediated killing and cytokine-driven inflammation, Type I relies on the rapid release of mediators from mast cells and the subsequent cascade of inflammatory events. Signup and view all the answers

Type ______ hypersensitivity is caused by CD4+ T cells reacting to an allergen.

I Signup and view all the answers

The ______ of IgE on the surface of mast cells results in the release of mediators.

cross-linking Signup and view all the answers

The release of mediators from mast cells can lead to ______ inflammation.

chronic Signup and view all the answers

CD8+ T cells can bind to ______ receptors on mast cells.

Fc Signup and view all the answers

The immediate hypersensitivity reaction typically occurs within ______ of allergen exposure.

hours Signup and view all the answers

The late-phase reaction in immediate hypersensitivity is characterized by the infiltration of ______ into the affected tissues.

eosinophils Signup and view all the answers

The primary function of IgE in Type I hypersensitivity is to bind to ______ cells.

mast Signup and view all the answers

The release of ______ from mast cells contributes to the symptoms of airway obstruction in allergic reactions like asthma.

histamine Signup and view all the answers

The ______ is the most abundant mediator generated by mast cells.

prostaglandin D2 Signup and view all the answers

The release of mediators from mast cells causes intense ______.

bronchoconstriction Signup and view all the answers

The ______ pathway is activated when an allergen is connected to a particular cell.

cyclooxygenase Signup and view all the answers

Exposure to allergens can cause ______ of the skin.

congestion Signup and view all the answers

Systemic exposure to allergens can lead to ______ reactions.

anaphylactic Signup and view all the answers

The release of mediators from mast cells can lead to increased ______ secretion.

mucous Signup and view all the answers

The ______ are immune cells responsible for presenting allergens to CD4+ T cells.

dendritic cells Signup and view all the answers

The ______ cells are responsible for the production of IgE antibodies.

plasma Signup and view all the answers

Immediate ______ reactions are initiated by the introduction of an allergen, which stimulates Th2 cells and immunoglobulin E (IgE) production.

hypersensitivity Signup and view all the answers

The complement system consists of several circulating and membrane ______ that play important roles in host defense.

proteins Signup and view all the answers

IgE binds to Fc ______ receptors (Fc εRI) on mast cells, and subsequent exposure to the allergen activates the mast cells to secrete the mediators.

receptors Signup and view all the answers

The complement system plays important roles in ______ and tissue injury in immunologic diseases.

inflammation Signup and view all the answers

IgE binds to ______ receptors (Fc εRI) on mast cells, and subsequent exposure to the allergen activates the mast cells to secrete the mediators.

Fc Signup and view all the answers

The ______ system consists of several circulating and membrane proteins that play important roles in host defense.

complement Signup and view all the answers

The __________ reaction occurs minutes after exposure to an allergen.

immediate Signup and view all the answers

The __________ phase reaction occurs 2–24 hours after repeat exposure to the allergen.

late Signup and view all the answers

Components such as __________ proteins play an essential role in Type II and III forms of hypersensitivity.

complement Signup and view all the answers

The sequence of events in immediate hypersensitivity follows the __________ exposure to the allergen.

initial Signup and view all the answers

Immediate hypersensitivity reactions are often mediated by the release of __________ from mast cells.

histamine Signup and view all the answers

In the context of hypersensitivity, __________ cells are primarily involved in mediating Type I hypersensitivity reactions.

mast Signup and view all the answers

LTC and LTD are the most potent vasoactive and ______ agents.

spasmogenic Signup and view all the answers

Cytokines are synthesized and secreted to ______ mast cell activation.

facilitate Signup and view all the answers

These include tumor necrosis factor (TNF) and ______.

chemokines Signup and view all the answers

Respiratory difficulty is caused by pulmonary ______ constriction.

bronchial Signup and view all the answers

In anaphylaxis, mediators released from mast cells can cause ______.

systemic Signup and view all the answers

In the late-phase response, the ______ phase is characterized by the influx of leukocytes.

inflammatory Signup and view all the answers

An increased level of ______ permeability during hypersensitivity reactions can lead to swelling.

vascular Signup and view all the answers

The primary role of eosinophils during allergic reactions is to ______ inflammation.

regulate Signup and view all the answers

Match the following hypersensitivity reactions with their characteristics:

Hypersensitivity = An overactive immune response Atopy = A type of hypersensitivity reaction that involves IgE antibodies Autoimmunity = The immune system's ability to distinguish between self and non-self Immune complex-mediated hypersensitivity = A type of hypersensitivity reaction that involves the formation of immune complexes Signup and view all the answers

Match the following cells with their roles in hypersensitivity reactions:

Mast cells = Release histamine and other mediators CD4+ T cells = Induce chronic inflammation in response to an allergen Dendritic cells = Present antigens to T cells Eosinophils = Release anti-inflammatory mediators Signup and view all the answers

Match the following mediators to their corresponding effects in an immediate hypersensitivity reaction:

Histamine = Increased vascular permeability and smooth muscle contraction Leukotrienes = Bronchospasm, vascular permeability, and mucus secretion Prostaglandins = Vasodilation, pain, and fever Cytokines = Recruitment and activation of inflammatory cells Signup and view all the answers

Match the following terms with their definitions:

Anaphylaxis = A severe, systemic allergic reaction Atopy = A type of hypersensitivity reaction that involves IgE antibodies Immune tolerance = The immune system's ability to distinguish between self and non-self Inflammation = A local immune response to tissue damage or infection Signup and view all the answers

Match the following mediators with their effects:

Histamine = Causes smooth muscle contraction and increased vascular permeability IgE = Triggers the release of histamine and other mediators from mast cells Leukotrienes = Causes bronchial constriction and increased mucus production Prostaglandins = Causes fever and pain Signup and view all the answers

Match the following types of hypersensitivity reactions with their characteristics:

Type I hypersensitivity = Involve IgE antibodies and immediate symptoms Type II hypersensitivity = Involve IgG or IgM antibodies and complement activation Type III hypersensitivity = Involve immune complexes and inflammation Type IV hypersensitivity = Involve T cell-mediated delayed reactions Signup and view all the answers

Match the following immune responses with their characteristics:

Acute inflammation = A local immune response to tissue damage or infection Chronic inflammation = A prolonged immune response to persistent infection or tissue damage Immune tolerance = The immune system's ability to distinguish between self and non-self Immunologic memory = The ability of the immune system to remember specific antigens Signup and view all the answers

Match the following immune cells with their roles in hypersensitivity reactions:

Th2 cells = Produce cytokines that promote IgE production Dendritic cells = Present antigens to T cells Eosinophils = Release granules that cause tissue damage Mast cells = Release histamine and other mediators Signup and view all the answers

Match the following terms with their definitions:

Allergen = A substance that triggers an allergic response Antigen = A substance that triggers an immune response Hapten = A small molecule that can trigger an immune response when bound to a carrier protein Immunogen = A substance that triggers an adaptive immune response Signup and view all the answers

Match the following characteristics with the corresponding phase of hypersensitivity reaction:

Vasodilation, congestion, and edema = Immediate reaction Inflammation rich in eosinophils, neutrophils, and T cells = Late-phase reaction Release of mediators from mast cells = Immediate reaction Systemic reaction = Late-phase reaction Signup and view all the answers

Match the following mediators with their primary function in hypersensitivity reactions:

Histamine = Causes smooth muscle contraction and increased vascular permeability Eosinophils = Rich in inflammatory infiltrate IgE = Binds to allergens and triggers mast cell degranulation T cells = Presents antigens to immune cells Signup and view all the answers

Match the following cells with their primary role in hypersensitivity reactions:

Mast cells = Release histamine and other mediators Eosinophils = Rich in inflammatory infiltrate T cells = Presents antigens to immune cells Neutrophils = Part of inflammatory infiltrate Signup and view all the answers

Match the following characteristics with the corresponding type of hypersensitivity reaction:

Antibody-mediated = Type II hypersensitivity Immune complex-mediated = Type III hypersensitivity Immediate hypersensitivity = Type I hypersensitivity Delayed-type hypersensitivity = Type IV hypersensitivity Signup and view all the answers

Match the following timing with the corresponding phase of hypersensitivity reaction:

Within minutes = Immediate reaction 2 to 24 hours later = Late-phase reaction Hours after exposure = Delayed-type hypersensitivity Days after exposure = Late-phase reaction Signup and view all the answers

Match the following morphological features with the corresponding phase of hypersensitivity reaction:

Vasodilation = Immediate reaction Congestion = Immediate reaction Edema = Immediate reaction Inflammation rich in eosinophils, neutrophils, and T cells = Late-phase reaction Signup and view all the answers

Match the following cells with their primary location in hypersensitivity reactions:

Mast cells = Tissue-bound Eosinophils = Inflammatory infiltrate T cells = Lymphoid organs Neutrophils = Bloodstream Signup and view all the answers

Match the following characteristics with the corresponding outcome of hypersensitivity reactions:

Upper airway obstruction = Systemic reaction Bronchial changes = Asthma Edema = Local reaction Inflammation = Late-phase reaction Signup and view all the answers

Match the following mediators with their effects:

Vasoactive amines = Cause central dysfunction: Anaphodies can also cause central dysfunction Cytokines = Produce functional decrements without cell or tissue injury Lipid mediators = Bind to and activate or inhibit receptors on the surface of cells, producing functional decrements = Bind to and deplete essential molecules, producing functional decrements with cell or tissue injury Signup and view all the answers

Match the following descriptions with the corresponding type of hypersensitivity:

IgE antibodies = Type I hypersensitivity Immune complexes = Type III hypersensitivity IgG or IgM antibodies = Type II hypersensitivity T cell-mediated = Type IV hypersensitivity Signup and view all the answers

Match the following cells with their roles in hypersensitivity reactions:

Mast cells = Release histamine and other mediators Eosinophils = Present antigens to T cells Dendritic cells = Activate T cells Th2 cells = Produce cytokines Signup and view all the answers

Match the following effects with the corresponding type of reaction:

Smooth muscle contraction = Immediate hypersensitivity reaction Increased vascular permeability = Late-phase reaction Eosinophil infiltration = Type I hypersensitivity Upper airway obstruction = Systemic immediate hypersensitivity reaction Signup and view all the answers

Match the following mediators with their effects on airway obstruction:

Histamine = Causes smooth muscle contraction Leukotrienes = Increases vascular permeability Prostaglandins = Causes smooth muscle relaxation Cytokines = Recruits eosinophils Signup and view all the answers

Match the following characteristics with the corresponding type of hypersensitivity:

IgE-mediated = Type I hypersensitivity Immune complex-mediated = Type III hypersensitivity Antibody-mediated = Type II hypersensitivity T cell-mediated = Type IV hypersensitivity Signup and view all the answers

Match the following cells with their roles in presenting antigens:

Dendritic cells = Present antigens to T cells Mast cells = Release histamine and other mediators Eosinophils = Present antigens to B cells Th2 cells = Produce cytokines Signup and view all the answers

Match the following types of hypersensitivity with their corresponding timing:

Type I hypersensitivity = Immediate reaction Type IV hypersensitivity = Delayed reaction Type II hypersensitivity = Antibody-mediated reaction Type III hypersensitivity = Immune complex-mediated reaction Signup and view all the answers

Match the following cytokines with their primary functions in Type I hypersensitivity reactions:

IL-4 = Stimulates B cell differentiation into IgE-producing plasma cells IL-5 = Activates eosinophils, contributing to inflammation IL-13 = Enhances mucus production and airway hyperresponsiveness TNF-alpha = Induces inflammation and tissue damage Signup and view all the answers

Match the following terms with their definitions in the context of Type I hypersensitivity:

Sensitization = Initial exposure to an allergen that primes the immune system Degranulation = Release of preformed mediators from mast cells Late-phase reaction = Delayed inflammatory response occurring hours after allergen exposure Atopic = Genetic predisposition to develop allergies Signup and view all the answers

Match the following mediators with their primary effects in Type I hypersensitivity reactions:

Histamine = Causes vasodilation, increased vascular permeability, and bronchoconstriction Leukotrienes = Contribute to bronchoconstriction, mucus production, and vascular permeability Prostaglandins = Induce vasodilation, pain, and inflammation Cytokines = Regulate the immune response and contribute to inflammation Signup and view all the answers

Match the following clinical manifestations with their corresponding Type I hypersensitivity reactions:

Anaphylaxis = Systemic, life-threatening reaction characterized by airway obstruction, hypotension, and shock Asthma = Chronic inflammatory airway disease characterized by bronchospasm, wheezing, and mucus production Atopic dermatitis = Chronic inflammatory skin condition characterized by itching, redness, and dryness Hay fever = Allergic rhinitis characterized by sneezing, runny nose, and itchy eyes Signup and view all the answers

Match the following cells with their roles in Type I hypersensitivity reactions:

Mast cells = Release mediators upon degranulation, contributing to the immediate reaction Eosinophils = Infiltrate the site of inflammation and contribute to tissue damage B cells = Produce IgE antibodies in response to allergen exposure T cells = Regulate the immune response and contribute to the development of allergies Signup and view all the answers

Match the following events with their order in the development of Type I hypersensitivity:

Sensitization = Initial exposure to an allergen Degranulation = Release of mediators from mast cells Late-phase reaction = Delayed inflammatory response Production of IgE antibodies = B cell differentiation into IgE-producing plasma cells Signup and view all the answers

Match the following characteristics with their corresponding types of hypersensitivity reactions:

Type I = Immediate, IgE-mediated Type II = Antibody-mediated, cytotoxic Type III = Immune complex-mediated Type IV = Cell-mediated, delayed Signup and view all the answers

Match the following conditions with their potential triggers of Type I hypersensitivity reactions:

Asthma = Dust mites, pollen, pet dander Atopic dermatitis = Food allergens, environmental allergens Anaphylaxis = Insect stings, medications, food allergens Hay fever = Pollen, mold, dust mites Signup and view all the answers

Study Notes

Type IV Hypersensitivity

Mediated by CD4+ T cells that produce delayed-type immune responses.
CD4+ T cells bind to IgE, leading to cross-linking of associated cells and chronic inflammation.
CD8+ T cells contribute to tissue damage by destroying target cells when activated.

Immediate vs. Late-phase Reaction

Immediate reaction occurs within minutes after allergen exposure, characterized by:
- Vascular effects, such as vasodilation and increased vascular permeability.
- Activation of mast cells leading to the release of mediators like histamine.
Late-phase reaction develops 2 to 24 hours later, with:
- Inflammatory infiltrates consisting mainly of eosinophils, neutrophils, and T cells.
- Increased mucus production and bronchial hyperactivity in cases like asthma.

Role of Mediators in Immediate Hypersensitivity

Three key groups of mediators include vasoactive amines, lipid mediators, and cytokines.
Histamine causes rapid vasodilation and increased vascular permeability, leading to symptoms such as edema.
Cytokines like IL-4 and IL-5 from T helper type 2 (Th2) cells amplify the immune response.

Effects of Allergens

Allergens, such as pollen, can trigger an array of hypersensitivity reactions.
Key clinical syndromes associated with immediate hypersensitivity include:
- Anaphylaxis: Severe reaction causing shock and airway obstruction.
- Bronchial asthma: Characterized by airway obstruction and inflammation due to smooth muscle hyperactivity.
- Allergic rhinitis: Increased mucus secretion leading to nasal congestion.

Antibody-Mediated (Type II) Hypersensitivity

Causes damage by IgG or IgM antibodies targeting antigens on cell surfaces.
Common disorders include autoimmune diseases, caused by the destruction of host tissue through immune mechanisms.

Immediate (Type I) Hypersensitivity

Involves abnormal reactions to typically harmless environmental antigens, known as allergens.
Mediated by Immunoglobulin E (IgE) antibodies that are produced upon first exposure to an allergen.
Mast cells are key players, releasing substances that cause inflammation, leading to symptoms of allergic reactions.
Common triggers include pollen, dust mites, animal dander, and certain foods.
Can cause excess reactions against microbes, contributing to allergic diseases, which are prevalent in urban areas.

Antibody-Mediated (Type II) Hypersensitivity

Triggered by IgE antibodies binding to specific antigens on cell surfaces.
This binding can destroy cells by activating complement pathways, promoting inflammation and functional abnormalities in tissues.
Primarily involves blood basophils and the destruction of targeted cells.

Immune Complex–Mediated (Type III) Hypersensitivity

Characterized by the formation of immune complexes (antibodies bound to antigens) that deposit in tissues.
Leads to complement activation and inflammation due to the accumulation of these complexes in vessels and tissues.
Involves mast cells and the release of mediators that exacerbate inflammation.

T Cell–Mediated (Type IV) Hypersensitivity

Involves CD4+ T helper cells and CD8+ cytotoxic T cells.
Activation of T cells leads to chronic inflammation and tissue damage.
Relies on cellular immunity rather than antibodies, differentiating it from other hypersensitivity reactions.

Immediate vs. Late-Phase Reactions

Initial exposure to an allergen stimulates Th2 cells, resulting in IgE production and mast cell activation.
Early symptoms are due to direct release of mediators from mast cells.
Late-phase reactions develop over hours and are characterized by prolonged inflammation involving other immune cells, such as eosinophils.

Complement System

Comprises circulating proteins that assist in host defense, inflammation, and tissue repair.
Plays a crucial role in antibody-mediated hypersensitivity (Type II) and immune complex-mediated hypersensitivity (Type III).
Activated through various pathways involving microbial components that enhance opsonization and phagocytosis of pathogens.

Key Functions of the Complement System

Opsonization: Coats pathogens to enhance phagocytosis.
Inflammation: Attracts immune cells to sites of infection through complement byproducts (C3a, C5a).
Cellular dysfunction: Antibodies can interfere with normal hormone receptor function, as seen in autoimmune conditions affecting the thyroid.

Conclusion

Understanding different hypersensitivity types is essential for diagnosing and managing allergic and autoimmune diseases.
Immediate hypersensitivity reactions can lead to significant clinical symptoms and long-term health impacts if not addressed appropriately.

Hypersensitivity Reactions Overview

Type IV hypersensitivity is a cell-mediated immune response involving CD4+ T cells and CD8+ T cells.
CD4+ T cells bind to IgE, leading to chronic inflammation via cross-linking of associated cells.
CD8+ T cells utilize Fc receptors to transmit intracellular signals that result in tissue damage.

Immediate and Late Reactions

Initial allergen exposure triggers immediate reactions, primarily mediated by mast cells and the secretion of inflammatory mediators.
Late-phase reactions involve eosinophils and vascular congestion, leading to edema and prolonged inflammation.

Mechanisms of Allergic Response

Pathogens may be intrinsic, like normal molecules in cellular membranes, or extrinsic like adsorbed exogenous antigens.
Cross-reactive antibodies to microbes or other antigens may provoke hypersensitivity.

Types of Hypersensitivity

Immediate hypersensitivity reactions are initiated by allergen exposure that stimulates Th2 cells and production of IgE.
IgE binds to Fc receptors (FcεRI) on mast cells; subsequent allergen exposure induces mast cell activation and mediator release.
Activation of the complement system plays a crucial role in inflammation and host defense through interactions with circulating proteins and membrane proteins.

T Cell-Mediated Hypersensitivity (Type IV)

Two main types of T-cell reactions that can cause tissue injury:
- Cytokine-mediated inflammation, mainly produced by CD4+ T cells, also known as delayed-type hypersensitivity.
- Cytotoxicity mediated by CD8+ T cells leading to direct tissue damage.

Immune Complex-Mediated Hypersensitivity (Type III)

Immune complexes formed in circulation may deposit in blood vessels, eliciting inflammatory responses.
Inflammation is primarily caused by CD8+ T cells interacting with the deposited immune complexes, leading to tissue injury and disease progression.

Immediate and Late-phase Reactions in Allergic Responses

Type IV hypersensitivity is mediated by CD4+ T cells, leading to chronic inflammation.
CD8+ T cells and Fc receptors contribute to destruction of effector cells in response to allergens.
Allergen exposure triggers immediate and late-phase reactions involving mast cells and other immune components.

Role of Mast Cells and Mediators

Mast cells are key players in immediate reactions, producing various mediators.
Release of mediators leads to vascular congestion, edema, and smooth muscle contraction.
Common mediators include leukotrienes LTC4 and LTD4 that induce vasodilation and bronchospasm.

Cytokines and Immune Activation

Cytokines are secreted from activated mast cells, influencing local immune responses.
Tumor Necrosis Factor (TNF) and chemokines are critical for recruiting leukocytes to sites of inflammation.
These processes can lead to respiratory distress, especially noticeable in conditions such as asthma.

Activation of the Complement System

The complement system plays a significant role in type II and type III hypersensitivity.
It consists of a series of proteins that aid in host defense and are involved in inflammatory responses.
Complement activation can result in tissue injury during immunologic diseases.

Anaphylaxis and Systemic Reactions

Anaphylaxis is a severe, systemic response to allergens like bee venom or certain drugs.
Symptoms may include hypotension, bronchospasm, and hives due to widespread mast cell activation.
Understanding the sequence of events in allergic reactions, including both immediate and late-phase responses, is crucial for effective management and treatment.

Immune Response and Hypersensitivity

Immune system malfunctions can lead to tissue injury and chronic diseases.
Hypersensitivity reactions can occur against normally harmless antigens in some individuals.
These reactions may cause severe complications, including morbidity and mortality.

Types of Hypersensitivity Reactions

Hypersensitivity reactions are classified into four major types based on the nature of the adaptive immune response.
Immediate hypersensitivity (Type I) involves IgE antibodies and mast cell activation, resulting in rapid allergic reactions.
Late-phase reactions occur hours after exposure, characterized by inflammation and immune cell infiltration.

Mechanisms of Hypersensitivity

Atopy is characterized by heightened sensitivity to environmental antigens, with defective protective mechanisms.
Cytokines IL-4, IL-5, and IL-13 play significant roles in mediating immunological tissue responses.
IL-4 stimulates B cells to produce IgE; IL-5 activates eosinophils which contribute to tissue inflammation.

Immediate Hypersensitivity

Immediate hypersensitivity arises through IgE-mediated activation of mast cells.
Symptoms develop within minutes and can include vasodilation, congestion, and edema.
Late-phase reactions show a rich infiltrate of eosinophils and neutrophils, indicating a sustained immune response.

Cellular Actions and Mediators

Three groups of mediators are important in immediate hypersensitivity: vasoactive amines, lipid mediators, and cytokines.
Tumor necrosis factor (TNF) and other mediators contribute to respiratory distress and may cause bronchoconstriction.
Anaphylaxis can occur due to systemic exposure to allergens, resulting in severe, life-threatening reactions.

Cytokine Roles and Cell Dysfunction

Cytokines influence cellular responses by binding to surface receptors and activating various immune cells.
Disorders can arise when antibodies interact with receptors, resulting in cellular dysfunction or tissue injury.
The cytokine environment significantly impacts both the magnitude and duration of the immune response.

Summary of Clinical Features

Immediate reactions can manifest with marked vascular and smooth muscle response to allergens.
A better understanding of these mechanisms facilitates targeted therapies for allergic and autoimmune conditions.
Recognizing the mechanisms involved helps in managing and preventing hypersensitivity reactions effectively.

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Description

Understand the mechanism of Type IV Hypersensitivity, a delayed-type immune response mediated by CD4+ T cells, and how it differs from immediate reactions.