Chapter 28: Hypersensitivities and Immunologic Disorders

Exam 4

How can the immune system cause serious conditions?

by overreacting or underreacting to stimuli

What is Immunopathology?

the study of disease states associated with over activity or under activity of the immune response

What is Hypersensitivity?

inappropriate immune response that results in host damage

What are the two major types of hypersensitivity?

• Antibody-mediated

• Cell-mediated

What is an allergy (allergic reaction)?

sensitivity to an allergen

An allergy usually involves what kind of antibody response?

IgE

An autoimmune disease targets what?

body tissues (self vs non-self fails here)

What is immunodeficiency?

a disorder that occurs when the immune system is too weak to prevent infection

Type 1 Hypersensitivities have a tendency to be what?

inherited

(Type 1 Hypersensitivities)

Documented reactions occur in at least what percent of the population?

20% to 30%

(Type 1 Hypersensitivities)

What occurs during the first exposure?

• B cells are activated and proliferated

• Class switching to IgE occurs

• IgE is produced by the plasma cell

(Type 1 Hypersensitivities)

What happens during sensitization?

the Fc portion of IgE binds to the mast cell receptors

(Type 1 Hypersensitivities)

During the second exposure, cell bound IgE molecules react with the antigen through?

cross-linking

(Type 1 Hypersensitivities)

During the second exposure, what does the mast cell release? What is the process called?

histamines and other inflammatory mediators; process is called degranulation

(Type 1 Hypersensitivities)

Second exposure yields what?

at rapid reaction including hives, hay fever, asthma, anaphylactic shock

Most allergic reactions are?

local anaphylaxis

What is localized anaphylaxis?

• hives

• hay fever

• asthma

What are hives?

allergic skin reaction characterized by the formation of wheal and flare rash

What is hay fever?

allergic condition caused by inhaled antigens

What are some symptoms of hay fever?

itching teary eyes, sneezing and running nose

What is asthma?

a respiratory allergy

In asthma, allergic mediators are attracted to an inflamed respiratory tract, what does this result in?

an increase in mucous secretion and bronchi spasm

Generalized/Systematic anaphylaxis is rare but?

more serious

In generalized/systematic anaphylaxis antigens enter where?

the bloodstream

What happens when antigens enter the bloodstream in generalized anaphylaxis?

the reaction spreads and affects almost the entire body; can also induce shock

What is shock?

a state in which blood pressure is too low to supply the required amount of blood flow

during generalized anaphylaxis massive release of mediators causes?

extensive blood vessel dilation and fluid loss which then causes a fall in pressure leading to flow insufficiency

(Type 1 Hypersensitivities)

what alters the immune response?

immunotherapy

(Type 1 Hypersensitivities)

Desensitization causes the immune system to what?

produce IgG

In desensitization, IgG binds to the antigen which prevents what?

IgE from binding to the mast cell

Desensitization involves what of an extremely dilute antigen over time?

injection

Omalizumab is a what?

rhuMab (Recombinant humanized Monoclonal antibody)

(Type 2 Hypersensitivities: Cytotoxic)

What are some examples?

blood transfusion reactions, hemolytic disease of a newborn, and some autoimmune diseases

(Type 2 Hypersensitivities: Cytotoxic)

Erythrocytes have what on the surface?

antigenic determinants

(Type 2 Hypersensitivities: Cytotoxic)

A major groups is ABO, which yields?

A, B, AB, or O blood types

(Type 2 Hypersensitivities: Cytotoxic)

individuals have ________ to the ________ they lack

antibodies, antigens

Type 2 Hypersensitivities are mostly which antibiotic class?

IgM

(Type 2 Hypersensitivities: Cytotoxic)

What is triggered when antibodies react with the antigen on the cell surface?

destruction of cells

(Type 2 Hypersensitivities: Cytotoxic)

What are the two methods of cell destruction

1. Activate classical pathway of complement systems which leads to lysis via membrane attack complexes (MACs)

2. Trigger antibody-dependent cellular cytotoxicity (ADCC) which leads natural killer (NK) cells to destroy cells

What is Hemolytic disease caused by?

the incompatibility of the Rh factor between mother and child

What does it mean when Rh is pos? What does it mean when it is neg?

Rh+ = Rh antigen is present

Rh - = Rh antigen is missing

(Hemolytic disease)

• mother is Rh-, fetus is Rh+

• Anti-Rh antibodies are produced in the pregnant mother with the Rh+ fetus

• First pregnancy: Rh+ fetus is unharmed

• Second pregnancy: Rh+ provokes strong secondary immune response

(Hemolytic disease)

Why does the fetus provoke the immune response in the second pregnancy?

because the IgG secondary response crosses the placenta which causes extensive damage to the red blood cells of the fetus

(Hemolytic disease)

RhoGAM contains what? What do these do? What do they prevent?

RhoGAM contains anti-Rh antibodies which bind to any Rh+ red blood cells that may have entered circulation during the first pregnancy

This prevents stimulation of the primary immune response

(Type 3 Hypersensitivities: Immune Complex-Mediated)

What is serum sickness?

it is a systemic immune complex reaction

(Type 3 Hypersensitivities: Immune Complex-Mediated)

What is serum sickness cause by?

passive immunization (antibodies provided for protection)

(Type 3 Hypersensitivities: Immune Complex-Mediated)

What is an arthus reaction?

it is a localized immune complex reaction

(Type 3 Hypersensitivities: Immune Complex-Mediated)

An arthus reaction occurs following?

injection of an antigen into a previously immunized individual with circulating antibodies

(Type 4 Hypersensitivities: Delayed Cell-Mediated)

Delayed hypersensitivities are caused by?

T-cell mediated immunity

(Type 3 Hypersensitivities: Immune Complex-Mediated)

Delayed hypersensitivities have a fast or slow developing response to the antigen?

slow

(Type 3 Hypersensitivities: Immune Complex-Mediated)

What are the T-cells responsible for?

reactions which can occur nearly anywhere in the body

(Type 3 Hypersensitivities: Immune Complex-Mediated)

Delayed hypersensitivity reactions are responsible for?

contact dermatitis, tissue damage, rejection of tissue grafts, and some autoimmune diseases

(Type 3 Hypersensitivities: Immune Complex-Mediated)

Some examples of causes?

nickel jewelry, leather, cosmetics, latex, poison ivy, and poison oak

(Type 3 Hypersensitivities: Immune Complex-Mediated)

What is the Tuberculin skin test?

it involves the introduction of small quantities of protein antigens from organism into skin

(Tuberculin skin test)

What happens if the skin test is positive?

the injection site will redden and gradually thicken; reaction reaches peak in 2-3 days

(Tuberculin skin test)

What does the reaction result from?

sensitized T cells that release cytotoxins causing an influx of macrophages

(Autoimmune Diseases)

How does the body recognize self antigens?

• destroys cells that would destroy self

• malfunction in immune recognition basis for autoimmunity

(Autoimmune Diseases)

What would cause autoimmunity to occur after tissue injury?

self antigens are released from the injured organ

autoantibodies form and interact with injured tissues

Autoimmune disease reactions occur over a spectrum from ________ to _________

organ-specific to widespread responses

What is an example of organ-specific?

Thyroid disease where only the thyroid is affected

What is an example of widespread response?

• Lupus where autoantibodies are made against nuclear constituents of all body cells (overload response)

• Rheumatoid arthritis: immune response is made against collagen in connective tissue