Immunity and Hypersensitivity Reactions

Vocabulary flashcards covering the basics of immunity, immunoglobulin types, primary and secondary immunodeficiencies, and the four types of hypersensitivity reactions.

Natural Immunity

An inflammatory response that does not require prior exposure to the offending agent (antigen); it is non-specific and lacks memory.

Acquired Immunity

A specific response to a specific antigen that requires a sensitizing exposure and is magnified by subsequent exposures.

IgA

Antibodies comprising about $10\%$ to $15\%$ of those in the body, found in the nose, digestive tract, ears, eyes, vagina, saliva, and tears to protect surfaces exposed to the outside.

IgG

The smallest but most abundant antibodies ($75\%$ to $80\%$) found in all body fluids; they are the only type that can cross the placenta to confer immunity to the fetus.

IgM

The largest type of antibody ($5\%$ to $10\%$) found in blood and lymph fluid; it is the first type produced in response to an infection.

IgD

Antibodies found in small amounts in tissues lining body cavities that play a role in allergic reactions to milk, medications, and poisons.

IgE

Antibodies found in the lungs, skin, and mucous membranes that help protect against substances like pollen and fungus spores; levels are often high in people with allergies.

Bruton X-linked Agammaglobulinemia

A genetic defect on the long arm of the X chromosome (Bruton’s tyrosine kinase) that typically appears in boys $<1$ year old, rendering B cells incapable of maturation.

DiGeorge Syndrome

A condition caused by defective development of the third and fourth pharyngeal pouches, resulting in interrupted T-cell maturation due to the absence of a functional thymus.

Severe Combined Immunodeficiency (SCID)

A group of over 20 disorders characterized by deficiencies in T-cell and B-cell development and function, often presenting with recurrent infections and failure to thrive in the first few months of life.

Immunodeficiency with Ataxia Telangiectasia

A condition where DNA repair is affected, leading to frequent sinopulmonary infections, balance problems, and widened small capillaries.

Chediak-Higashi Syndrome

An autosomal recessive disorder causing defective fusion of lysosomes and phagosomes, leading to albinism and increased susceptibility to pyogenic bacteria.

Wiskott-Aldrich Syndrome

An X-linked disorder characterized by reduced platelet numbers and function, alongside reduced T and B cell numbers.

Leukocyte Adhesion Deficiency (LAD) Type I

A deficiency in integrins leading to localized, potentially life-threatening bacterial infections.

Leukocyte Adhesion Deficiency (LAD) Type II

A deficiency in selectins leading to life-threatening infections and severe developmental delay.

Type 1 Hypersensitivity

Immediate hypersensitivity mediated by IgE antibodies binding to mast cells and basophils, causing degranulation and the release of histamine.

Type II Hypersensitivity

Cytotoxic hypersensitivity where IgG and IgM antibodies bind to fixed cell surface antigens, often triggering complement activation and tissue damage.

Type III Hypersensitivity

Immune Complex Mediated hypersensitivity where IgG and IgM bind to circulating antigens forming meshworks (IC) that deposit in tissues like the kidneys or joints.

Type IV Hypersensitivity

Delayed-type hypersensitivity mediated by CD4+ T cells and cytokines (IL-1, IL-6, IL-12) that occurs $24-48$ hours after exposure.

Anaphylaxis

A Greek term meaning ‘excessive protection,’ describing a severe Type 1 hypersensitivity reaction triggered by subsequent exposure to an antigen after initial IgE production.

Goodpasture's Syndrome

A Type II hypersensitivity example involving anti-glomerular basement membrane antibodies.

Hashimoto's thyroiditis

A Type II hypersensitivity characterized by a nonhyperthyroid large goiter and anti-thyroglobulin antibodies.

Grave's Disease

An autoimmune thyroiditis (Type II hypersensitivity) caused by anti-TSH-Receptor antibodies leading to hyperthyroidism.

Myasthenia Gravis

A Type II hypersensitivity involving anti-acetylcholine receptor antibodies, which blocks natural ligand activity and leads to paralysis.

Systemic Lupus Erythematosis (SLE)

A systemic autoimmune disease that is a classic example of Type III (Immune Complex Mediated) hypersensitivity.