Hypersensitivities - an Antigenic Response Beyond What Is Normal

Immune Disease

Hypersensitivities - an antigenic response beyond what is normal. Immunodeficiency – the absence of sufficient immune response

Hypersensitivities 1. Type I – rapidly developing symptoms, common allergies Initial exposure sensitizes, subsequent exposure causes harmful allergic reactions.

Can be systemic, localized.

Anaphylaxis – acute multi-system reaction to allergen.

Sometimes results in Anaphylactic shock – IgE is produced against antigen, binds to mast cells and causes the release of immunological mediators (like histamine, prostaglandins) which lead to systemic vasodilatation and possible shock. Can cause death in minutes.

Examples –

2. Type II – antibodies bind abnormally to body cells, causing a reaction against cell/tissue surfaces.

Resulting in:  Altered cell function  Complement activation, cell lysis may occur  IgM may cause blood clumping

1 Autoimmune disease – where antibodies are produced against the body’s own tissues. Results in damage to one’s own organs.

ABO blood group reactions

Hemolytic disease of the newborn –  Rh+ carries antigen

 Only produced if Rh- mother is exposed to Rh+ (Rh- mother, Rh+ father) o first time sensitizes o second Rh+ child causes attack on fetus

 Rhogam

2 3. Type III – IgG and IgM react with body cells but those reacting body components are soluble in circulation so remain free to circulate.

 Antigen-antibody complex deposited in tissues, causing inflammation

 Examples –

4. Type IV – Cell mediated hypersensitivity (delayed)  Not triggered by antibodies but by T cells

 Examples –

Organ Transplantation HLA – histocompatability antigens Cyclosporine – immunosupression

• Autograft – from self

• Isograft – from identical individual

• Allograft – genetically different, same species

• Xenograft – different species

Immunodeficiencies  Congenital – at birth o SCID – Severe Combined Immunodeficiency

3  Acquired o Cancer – represents the failure of body system defenses, including the immune system

. Immunological surveillance theory

o AIDS – Acquired Immunodeficiency Syndrome History –

Morphology of virus

Stages of AIDS o Category A asymptomatic, swollen lymph nodes

o Category B persistent Candida infections

o Category C or clinical AIDS classified by T cell count, less than 200 is active

Prevention