Immunology Basics Quiz

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Questions and Answers

Which component of the immune system serves as a physical barrier against pathogens?

Lymphatic system

White blood cells

Skin (correct)

Complement proteins

What is the primary role of the immune system in rejecting foreign cells?

To remove worn-out cells from circulation

To identify and destroy abnormal cells (correct)

To protect against invading pathogens

To promote inflammation

Which of the following activities is NOT considered a function of immunity?

Rejection of foreign cells

Production of antibodies

Promotion of tissue repair (correct)

Defense against pathogens

What type of immune response involves an overreaction to harmless substances?

Hypersensitivity reaction Signup and view all the answers

What is the main function of the liver in the immune system?

Production of complement proteins Signup and view all the answers

What mediates the immediate response in Type I hypersensitivity reactions?

Primary mast cell mediators Signup and view all the answers

Which of the following is NOT considered a primary mast cell mediator?

Prostaglandins Signup and view all the answers

Which of the following events characterizes the delayed phase of Type I hypersensitivity?

Tissue damage and intense infiltration by inflammatory cells Signup and view all the answers

During a recurrent exposure in Type I hypersensitivity, which effect is primarily associated with mast cell degranulation?

Bronchoconstriction Signup and view all the answers

Which factor is primarily responsible for chemotaxis in a Type I hypersensitivity reaction?

Neutrophil chemotactic factor Signup and view all the answers

What is the role of Th2 cells in the immune response?

Activate eosinophils and phagocytosis. Signup and view all the answers

Which type of hypersensitivity is characterized by the immediate release of IgE antibodies?

Type I hypersensitivity Signup and view all the answers

When should immune responses typically be turned off?

When pathogens are fully eradicated. Signup and view all the answers

What primarily causes tissue damage in hypersensitivity reactions?

Antigen-antibody complexes. Signup and view all the answers

Autoimmune diseases involve immune responses that are directed against what?

The body’s own tissues. Signup and view all the answers

Which type of hypersensitivity reaction is classified as delayed-type?

Type IV hypersensitivity Signup and view all the answers

What can result from improperly regulated immune responses?

Anaphylactic shock Signup and view all the answers

What distinguishes immunodeficiency diseases from other disorders of immunity?

Diminished immune function. Signup and view all the answers

What is the primary distinction between innate immunity and adaptive immunity in terms of time response?

Innate immunity has a quicker response with no time lag. Signup and view all the answers

Which of the following is NOT a characteristic of innate immunity?

It is antigen specific. Signup and view all the answers

Which cell type is primarily associated with the cell-mediated response in adaptive immunity?

T cytotoxic lymphocytes Signup and view all the answers

Which of the following cells is NOT derived from the lymphoid progenitor in the immune system?

Monocytes Signup and view all the answers

What is the role of natural killer cells in innate immunity?

They identify and destroy virus-infected cells. Signup and view all the answers

Which type of proteins are predominantly formed in the liver and are involved in the immune response?

Complement proteins Signup and view all the answers

Which is a function of the humoral response in adaptive immunity?

Produce antibodies against specific pathogens. Signup and view all the answers

Which of the following statements about the immune system is accurate?

Innate immunity provides rapid, broad defenses against infections. Signup and view all the answers

What is the significance of hematopoietic stem cells in the immune system?

They give rise to all types of immune cells. Signup and view all the answers

Which of the following features defines adaptive immunity?

It involves memory and is antigen-specific. Signup and view all the answers

Which of the following is NOT a clinical manifestation of systemic anaphylaxis?

Wheezing Signup and view all the answers

What distinguishes Type II hypersensitivity reactions from Type I?

Direct cell lysis mediated by IgG or IgM antibodies Signup and view all the answers

In the context of local anaphylaxis, which of the following conditions is primarily associated with urticaria?

Food allergies Signup and view all the answers

Which mechanism is responsible for tissue damage in complement-dependent reactions of Type II hypersensitivity?

Activation of the complement system Signup and view all the answers

Which example illustrates the antibody-dependent cell-mediated cytotoxicity (ADCC) mechanism?

Lysis of parasites by NK cells Signup and view all the answers

Which type of hypersensitivity reaction typically involves patients experiencing hay fever?

Type I hypersensitivity Signup and view all the answers

In Type II hypersensitivity, which outcome is primarily caused by opsonization?

Enhanced phagocytosis Signup and view all the answers

Which of the following statements accurately describes the reaction to bee sting allergy in the context of Type I hypersensitivity?

It can lead to systemic manifestations like shock. Signup and view all the answers

What is the primary mechanism of action in a Type II hypersensitivity reaction?

Antibodies directed against cell surface receptors Signup and view all the answers

What is a clinical manifestation of Rhesus incompatibility in pregnancy?

Progressive anemia in the fetus Signup and view all the answers

In what condition do antibodies against acetylcholine receptors lead to impaired muscle function?

Myasthenia gravis Signup and view all the answers

Which of the following best describes Type III hypersensitivity?

Immune complex formation in the bloodstream Signup and view all the answers

Which of the following is a treatment method for erythroblastosis fetalis?

Administration of anti-D immunoglobulin Signup and view all the answers

What complication can arise from elevated bilirubin levels in newborns?

Kernicterus Signup and view all the answers

Autoimmune hemolytic anemia is classified under which type of hypersensitivity?

Type II Hypersensitivity Signup and view all the answers

Which pathology is characterized by the development of antibodies against the TSH receptors?

Grave's disease Signup and view all the answers

What is a primary feature of pemphigus vulgaris?

Autoimmune blistering skin disease Signup and view all the answers

What is a common outcome of untreated hemolytic anemia in patients?

Ischemia and organ damage Signup and view all the answers

Study Notes

Immunopathology I: Immune System & Hypersensitivity

The immune system is a functional system, not an organ system, encompassing various components.
Key components include: skin, mucus membranes, secretions (tears, mucus), blood cells, vasculature, bone marrow (WBC production), liver (complement proteins), lymphatic system, and lymphoid organs.
Most tissues contain immune cells.

Objectives

Understanding the basics of immune response.
Identifying common types of immune response.
Exploring cellular involvement in immune responses.
Outlining immune defense mechanisms.
Defining and clarifying auto-immune processes.
Describing major hypersensitivity reactions.

Immunity

Immunity is the body's ability to resist or eliminate potentially harmful foreign materials or abnormal cells.
Immune activities include defense against pathogens, removal of worn-out cells and debris from injuries/disease, identification and destruction of abnormal/mutant cells, rejection of foreign cells (like organ transplant), and appropriate responses to allergens or autoimmune diseases.

Overview of the Immune System

The immune system is divided into innate (non-specific) and adaptive (specific) components.
Innate immunity is the first line of defense, with a rapid response that's not antigen-specific and lacks memory.
Adaptive immunity is the second line of defense, with a slower response, antigen-specific components, and memory. Interaction between both is critical.

A Typical Immune Response

Innate immunity rapidly responds to a wide range of microbes, including external (skin, mucus membranes, secretions) and internal (phagocytic cells, antimicrobial proteins) defenses.
Acquired immunity has a slower response targeting particular microbes such as B lymphocytes (humoral and antibodies) and T lymphocytes (cell-mediated cytotoxic response).

Innate vs. Adaptive Immunity

Innate immunity has no time lag, is not antigen-specific, and does not have memory.
Adaptive immunity has a delay (at least 2-3 weeks) in response, is antigen-specific, and has memory (important for vaccinations).

Cells of the Immune System

Hematopoiesis is the process of blood cell production in bone marrow, originating from hematopoietic stem cells (pluripotent).
Key cells include lymphocytes (B cells, T cells, NK cells), myeloid progenitor cells (polymorphonuclear leukocytes, monocytes, and dendritic cells), and erythroid progenitor cells (platelets and erythrocytes).

Lymphoid Cells

Lymphoid progenitors give rise to cells critical in immune function.
B cells produce antibodies.
T cells are involved in cellular immune responses (activated T cells, helper T cells, cytotoxic T cells).
NK cells directly kill non-self or infected cells.
These cell types use CD markers (CD3, CD4, CD8, CD53) as surface markers for differentiation and function.

T & B Lymphocytes

T lymphocytes (T cells) have a long lifespan (70% of blood lymphocytes), form rosettes with sheep RBCs, and are characterized by a smooth surface and CD3 markers.
B lymphocytes (B cells) have a short lifespan (25% of blood lymphocytes), contain surface immunoglobulins (Ig's) and surface markers like CD19 and CD20.

Organs of the Immune System

Primary (central): bone marrow (B-cell generation), thymus (T-cell maturation).
Secondary (peripheral): lymph nodes (lymphocyte activation), spleen, mucosa-associated lymphoid tissue (MALT), tonsils, adenoids, and Peyer's patches (antigen encounters).

General Scheme of Immune Response to Tissue Antigen

Antigens are trapped in lymph nodes via afferent lymphatics.
Naive lymphocytes continuously circulate from blood to lymph nodes.
Activation of immune cells occurs upon encountering the antigen to target antigen source, resulting in eradication.

Antigen—Ag (Immunogen)

An antigen (immunogen) is any substance stimulating the immune system to produce antibodies.
Antigens, typically proteins, exhibit high molecular weight.
Complete antigens are usually foreign proteins with distinctive points (epitopes) inducing an immune response.
Incomplete antigens (haptens) lack inherent antigenic properties and gain this property on interaction with a carrier molecule.
Heterophilic or cross-reacting antigens share similar epitopes, initiating a response.

Antigen Stimulation of T-cells

Antigen-presenting cells (APCs, like macrophages) internalize and process antigens in association with MHC molecules.
Processed antigens are presented to T cells (differentiated T and B cells) with specific receptors, initiating immune responses.
MHC class I presents intracellular antigens to CD8+ T cells mediating cellular cytotoxicity.
MHC class II presents extracellular antigens to CD4+ T cells enabling cytokine-mediated responses.

Lymphokines

Lymphokines are proteins secreted by lymphocytes affecting cellular activities.
- Chemotactic factor, migration inhibitor factor, mitogenic factor, transfer factor, cytotoxic factor, interferons, and skin-reactive factor are examples involved in a cascade of immune responses.

Antigens Stimulation of B-cells

B cells recognize antigens through antigen receptors on their surface.
When triggered by T cells (and cytokines released by T cells), B cells proliferate and differentiate into antibody-producing plasma cells.
Memory B cells also play a crucial role by providing rapid and strong response upon re-exposure to the same antigen.

Antibody (Immunoglobulins—Ig)

Antibodies, produced by plasma cells, are proteins specifically targeting and reacting with antigens that triggered their production.
Antibody types (functional classification) include agglutinins (clumping of soluble antigens), precipitins (precipitating soluble antigens), neutralizing antibodies (neutralizing toxins/enzymes), and opsonins (coating antigens for enhanced phagocytosis) and complement-fixing antibodies.

Antibody Classification (Structural)

Immunoglobulins (Igs) are classified based on their structure. Specific Igs like IgM, IgG, IgA, IgE, and IgD play distinct roles in immune responses.

Pathogens

Extracellular pathogens (bacteria, bacterial products, parasites) stimulate B cells and Th2 cells, triggering antibody production.
Intracellular pathogens (intracellular bacteria, viruses) stimulate Th1-cells and CD8+ CTLs initiating cytokine-mediated phagocytosis or cellular cytotoxicity respectively.

Regulation of Immune Response

Immune responses need to be turned off (when the antigen is removed).
Improper regulation contributes to autoimmune diseases, hypersensitivity reactions, and tissue damage/necrosis.

Disorders of Immunity

Disorders affecting immune responses can include hypersensitivity reactions, autoimmune diseases, or immunodeficiency diseases.

Hypersensitivity

Hypersensitivity involves undesirable reactions from the normal immune system with potential causes being misdirected or amplified immune reactions.
These reactions are categorized into four types based on immune mechanisms leading to tissue damage: Type I (immediate), Type II (cytotoxic), Type III (immune complex), and Type IV (delayed).

Hypersensitivity Type I

Known as immediate or anaphylactic hypersensitivity, often called allergy.
Mediated by IgE antibodies.
Allergens (house dust, pollen, cosmetics, or food) trigger IgE production on mast cells.
Recurrent exposure leads to mast cell degranulation causing vasodilation, bronchoconstriction, and other reactions.
Two phases: primary rapid response and secondary delayed.
Can be systemic (anaphylaxis) or localized (allergic rhinitis, asthma).

Hypersensitivity Type II

Cytotoxic hypersensitivity, involving IgG or IgM antibodies targeting cell-surface antigens.
Complement system activation results in cell lysis or damage.
Mediated by complement-dependent reactions or antibody-dependent cell-mediated cytotoxicity (ADCC) causing target cell death.
Examples include transfusion reactions, hemolytic anemias, and Grave's disease.

Hypersensitivity Type III

Immune complex hypersensitivity, involving the formation of antigen-antibody complexes that deposit in tissues.
Activation of the complement system leads to inflammation, tissue damage, and possible organ damage.
Examples include acute serum sickness and certain types of glomerulonephritis.

Hypersensitivity Type IV

Delayed-type hypersensitivity or cell-mediated hypersensitivity triggered by T lymphocytes.
Response occurs hours or days after exposure to the antigen.
Involves T cells and macrophages.
Delayed hypersensitivity plays a role in defense against intracellular pathogens (like tuberculosis) as well as graft rejection and tumor immunity

Granuloma Formation

Granulomas are a form of chronic inflammation with macrophages and T cells forming a protective barrier.

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Description

Test your knowledge of immunology with this quiz covering key concepts such as immune system functions, hypersensitivity reactions, and the role of various cells in immunity. Challenge yourself to correctly answer questions about immediate and delayed immune responses, as well as specific mediators involved in hypersensitivity.