Human Physiology Week 2c - Hypersensitivity

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Questions and Answers

What is characterized as an exaggerated immune response in the body?

Normal immune response

Tolerance

Autoimmunity

Hypersensitivity (correct)

Which term is synonymous with type 1 hypersensitivity?

Systemic hypersensitivity

Atopy (correct)

Autoimmune syndrome

Delayed hypersensitivity

When a person with an allergy to pet dander is exposed, what kind of reaction occurs?

Chronic inflammation

Immediate hypersensitivity (correct)

Delayed hypersensitivity

Autoimmune response

Which of the following is considered a common trigger for type 1 hypersensitivity?

Dust mites Signup and view all the answers

What might happen to an individual experiencing type 1 hypersensitivity upon exposure to an allergen?

Release of hives Signup and view all the answers

What is atopic dermatitis primarily characterized by?

Inflammation triggered by an allergic response Signup and view all the answers

Which type of cell is responsible for presenting the allergen to T cells during a type 1 hypersensitivity reaction?

Dendritic cells Signup and view all the answers

What role does IgE play in type 1 hypersensitivity reactions?

It binds to mast cells to mediate allergic reactions. Signup and view all the answers

Which of the following is a common effect of histamine released from mast cells during an allergic reaction?

Constriction of smooth muscles in the bronchi Signup and view all the answers

What is the primary substance that leaks into tissues, increasing vascular permeability during an allergic reaction?

Water and plasma proteins Signup and view all the answers

What leads to the inappropriate response of the immune system towards its own cells?

Similarities between antigens on pathogens and self-antigens. Signup and view all the answers

What is the role of neutrophils in the context of type II hypersensitivity?

They become activated and recruit other immune cells. Signup and view all the answers

What is a possible outcome of the immune system's cross-reaction with self-antigens?

Inflammation and potential tissue injury. Signup and view all the answers

What can happen in some cases of type II hypersensitivity, aside from tissue destruction?

Reduction in the functionality of the affected tissues. Signup and view all the answers

How does the immune system recognize self-antigens inappropriately during type II hypersensitivity?

By confusing self-proteins with pathogen-related antigens. Signup and view all the answers

What is the immediate phase of type 1 hypersensitivity primarily mediated by?

Histamine release Signup and view all the answers

Which type of hypersensitivity reaction involves antibody-antigen complexes that clog blood vessels?

Type III hypersensitivity Signup and view all the answers

What can occur during the late phase reaction of type 1 hypersensitivity?

Increased mucus production Signup and view all the answers

Which cells are involved in the immediate reaction of a type 1 hypersensitivity event?

Mast cells Signup and view all the answers

During a type III hypersensitivity reaction, what happens to the antibody-antigen complexes?

They bind to blood vessel walls Signup and view all the answers

What triggers the late phase of a type 1 hypersensitivity reaction?

Persistent cytokine activity Signup and view all the answers

What is the primary immune response that type II hypersensitivity is characterized by?

Antibody production against self-antigens Signup and view all the answers

What is primarily affected in type IV hypersensitivity reactions?

T cells Signup and view all the answers

How long after exposure does type IV hypersensitivity typically manifest?

48 to 72 hours Signup and view all the answers

Which of the following is an example of type IV hypersensitivity?

Organ transplant rejection Signup and view all the answers

What happens during the immune response in type II hypersensitivity?

Antibodies bind to self-antigens Signup and view all the answers

What cellular mechanism contributes to tissue damage in delayed-type hypersensitivity?

Cytotoxic T-cell responses Signup and view all the answers

In the context of organ transplants, what role do immunosuppressants play?

Prevent type IV hypersensitivity reactions Signup and view all the answers

What is the main consequence of forming antibody-antigen complexes in blood vessels?

Clogging of blood vessels Signup and view all the answers

Which type of hypersensitivity reaction is characterized by a rapid response to allergens?

Type I hypersensitivity Signup and view all the answers

What type of cell is typically involved in mediating type I hypersensitivity?

Basophils Signup and view all the answers

What is an important factor in determining whether a person develops a rash from poison ivy?

Individual sensitivity to the allergen Signup and view all the answers

Study Notes

Hypersensitivity Overview

Hypersensitivity is characterized by an exaggerated immune response to typically harmless substances, called allergens.
Common allergens include pet dander, dust mites, and shellfish.
Allergic reactions can manifest through symptoms like hives, asthma, and anaphylaxis.

Types of Hypersensitivity Reactions

Four distinct types of hypersensitivity reactions are defined in immunology.

Type I Hypersensitivity (Immediate Hypersensitivity)

Also known as atopy; commonly linked to allergies.
Triggered by allergens, prompting an IgE-mediated response.
Dendritic cells present allergens to T helper cells, activating B cells to produce IgE antibodies.
IgE binds to mast cells, leading to degranulation and histamine release, which causes:
- Bronchial smooth muscle spasms and mucus production.
- Increased vascular permeability, leading to edema and inflammation.
Features an immediate reaction (15-30 minutes post-exposure) and a late-phase reaction (hours later) due to cytokine release, causing prolonged symptoms.

Type II Hypersensitivity (Antibody-Mediated)

Involves antibodies directed against self-antigens on host cells.
Can lead to cell destruction or dysfunction through:
- Complement activation and recruitment of immune cells.
- Binding and modifying self proteins, causing immune responses.

Type III Hypersensitivity (Immune Complex-Mediated)

Characterized by the formation of antibody-antigen complexes circulating in the blood.
These complexes can accumulate in blood vessels, leading to obstruction and inflammatory damage to vessel walls.
Associated with conditions like autoimmune diseases, where tissue necrosis due to inflammation occurs.

Type IV Hypersensitivity (Cell-Mediated)

Also known as delayed-type hypersensitivity; typically begins 48-72 hours after exposure.
Involves T-cells recognizing and responding to specific antigens, leading to tissue damage.
Common examples include:
- Organ transplant rejection, where T-cells attack foreign donor tissues.
- Contact dermatitis, like reactions to poison ivy.

Key Points to Remember

Anaphylactic reactions can evolve, requiring monitoring for delayed-phase symptoms.
Immunosuppressants are often necessary post-transplant to prevent Type IV hypersensitivity reactions.
Not all individuals exposed to potential allergens will develop hypersensitivity; predisposition plays a significant role.### Immune Response and Hypersensitivity Mechanisms
Macrophages can phagocytize invading cells, such as bacteria or fungi, engulfing them in a process called phagocytosis.
Phagocytized cells present antigens, which are proteins on their surface, to other immune cells, converting into antigen presenting cells.
The immune system may mistakenly confuse these antigens with similar-looking self-antigens, leading to inappropriate immune responses.
Cross-reactivity can occur where antibodies developed against external antigens mistakenly target the body’s own cells.
Types II hypersensitivity can result in tissue injury due to these misidentifications, leading to inflammation and cellular damage.

Mechanisms of Type II Hypersensitivity

Antibodies directed against self-antigens can either destroy tissue or impair functionality without destruction.
Thyroid cells can be affected by antibodies targeting the thyroid-stimulating hormone (TSH) receptor, causing inappropriate hormone production.
In certain cases, antibodies may either block receptor activity or mislead the receptor into an active state, resulting in uncontrolled hormonal release or dysfunction.
Myasthenia gravis occurs when antibodies block acetylcholine receptors at neuromuscular junctions, impeding muscle contraction which leads to muscle weakness.

Anaphylaxis Reaction

Anaphylaxis is a severe type I hypersensitivity reaction characterized by systemic responses to allergens, potentially life-threatening.
Histamine release from mast cells can lead to symptoms such as increased vascular permeability, resulting in fluid loss from the bloodstream and swelling (edema).
Symptoms include bronchoconstriction which causes difficulty breathing, systemic edema, and swelling of tissues like the tongue.
Treatment involves the administration of epinephrine, which counteracts histamine's effects by relaxing bronchioles, reducing vascular permeability and increasing heart rate to compensate for blood volume loss.

Allergic Reactions and Histamine Effects

Type I hypersensitivity reactions typically produce swelling such as hives, nasal congestion, and increased mucus production due to histamine activity.
Common symptoms are watery eyes, mild bronchoconstriction, and increased coughing.
Antihistamines, such as Benadryl, are used to block histamine’s action, alleviating allergic symptoms and reversing histamine-induced effects.

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Description

This quiz explores the concept of hypersensitivity, an exaggerated immune response. Using humorous analogies, it highlights the characteristics and effects of hypersensitivity in the immune system. Test your understanding of this fascinating topic!