Allergies

What are the two major categories of immune dysfunction?

Hypersensitivity and hyposensitivity diseases.

What is hypersensitivity?

An over-reactive immune response.

What is hyposensitivity?

An under-reactive immune response caused by incompletely developed, suppressed, or destroyed immune function.

What are the four types of hypersensitivity?

Type I, Type II, Type III, and Type IV.

What is Type I hypersensitivity?

An immediate allergic reaction involving IgE, mast cells, and basophils.

What is Type II hypersensitivity?

Antibody-mediated reactions, such as blood type incompatibilities.

How does Type II hypersensitivity damage cells?

IgG or IgM antibodies and complement proteins cause host cell lysis.

What is Type III hypersensitivity?

An immune complex disorder, such as rheumatoid arthritis.

How does Type III hypersensitivity cause inflammation?

IgG antibodies deposit in target-organ basement membranes.

What is Type IV hypersensitivity?

A T-cell-mediated reaction, such as graft rejection.

What happens during Type IV hypersensitivity?

T cells respond to self antigens or transplanted cells.

What are the two types of immunodeficiency?

Primary and secondary immunodeficiency.

What causes primary immunodeficiency?

Genetic disorders, such as SCID.

What causes secondary immunodeficiency?

Infections, metabolic disease, chemotherapy, radiation, or cancers.

What is an example of secondary immunodeficiency?

AIDS.

What is an allergy?

Inflammation in response to an allergen.

What is an allergen?

An environmental antigen that does not affect non-allergic individuals.

What are four routes or sources of allergens?

Inhalants, ingestants, injectants, and contact allergens.

What is sensitization?

The initial immune response that produces IgE and prepares cells for later allergen exposure.

Which cells initially recognize allergens?

B cells and T cells.

Which antibody is involved in Type I allergies?

Immunoglobulin E (IgE).

Which cells bind IgE and release allergic mediators?

Mast cells and basophils.

What is a major chemical mediator of allergic symptoms?

Histamine.

What happens first during sensitization?

An allergen enters, and a lymphatic vessel carries it to a lymph node.

What happens to B cells during sensitization?

With helper T-cell support, B cells proliferate into plasma cells.

What do plasma cells produce during sensitization?

IgE antibodies.

What happens to IgE after it is produced?

It binds to receptors on mast cells and basophils.

What happens during a second exposure to the allergen?

The allergen binds IgE on sensitized mast cells, triggering degranulation.

What is degranulation?

The release of chemical mediators from mast cells or basophils.

What can allergic mediators do to blood vessels and skin?

Dilate vessels, increase blood flow, and cause skin symptoms.

How can Type I allergies affect the respiratory system?

Bronchoconstriction, mucus buildup, and asthma symptoms.

How can Type I allergies affect the digestive system?

Increased intestinal movement, diarrhea, and vomiting.

How can Type I allergies affect the nervous system?

They can cause headache and pain.

What are four Type I allergic conditions?

Hay fever, asthma, eczema, and food or drug allergies.

What is the hygiene hypothesis in the lecture?

Reduced immune stimulation early in life may contribute to Type I allergies.