Allergic Response

IgE Mediated

Immediate response

Mediates the Type I allergic response

Has special F_c that attaches to mast cells (1st exposure)

Second exposure: allergen binds to two IgE receptors simultaneously which triggers mast cells to release histamine, prostaglandins, and other cytokines

What IgE binds to during allergic response during the first exposure

Releases histamine, prostaglandins, and other cytokines when two allergens bind to two IgE receptors

Released during the second exposure of an allergen

Two allergens bind simultaneously to IgE receptors on mast cell and the mast cell releases those chemicals

Occurs during the first exposure to an allergen

Mucus membrane class switch to IgA and IgE from IgM

Injected (not oral) allergen in small and gradually increasing doses causes serum B cells to produce IgG

IgG competes with IgE for binding to allergen to prevent the release of histamines and cytokines

 Or you can use anti-IgE antibodies (to F_c part of IgE) to neutralize IgE so it can't bind to mast cells

Peanut allergy

Causes smooth muscle dilation, dilators expand capillaries, diapedesis, hypovolemia, shock, and then death

Classic Type I HS

Generalized reaction in the mucous membrane in nasal passages

Cytotoxicity HS

Involves killing cells that express foreign antigens

Antibody mediated via complement or NK cells

Small molecule (hapten) binds to cell surface, or cells with different (non-self) surface proteins are introduced into the blood (blood transfusion)

The small molecule that binds to the cell surface

Elicits a type II HS response (cytotoxicity)

Isn't strong enough to elicit an immune response

Antibodies direct kiling of cells which they are bound to

Antibody-Dependent Cell-Mediated Cytotoxicity

When the Mom is Rh- and the baby is Rh+

Baby's blood comes in contact with mom's at birth or with leaky placenta

Rh factor is foreign to mom and she'll make IgM --> IgG

A second Rh+ baby will elicit a secondary immune response which can kill the baby's blood cells

Anti Rh injected into the mom for HDN during and after Rh+ birth

The anti Rh binds baby's blood and prevents mom from becoming Rh- sensitized

Immune complex disease

Mediated by Ab/Ag agglutination into complexes

Complexes get stuck in the basement membrane of the blood vessels

Causes neutrophils to release digestive enzymes at blood vessel epithelial cells

Ab/Ag agglutination that turns into complexes

A part of Type III HS

In a precipitation test, the presence of uncombined antigen above that required to combine with all of the antibody; precipitation may be inhibited because the presence of excess antigen gives rise to soluble antigen-antibody complexes

type III

Where the complexes stick to in blood vessels

Type III

Caused by activated complement

Neutrophils release the enzymes responsible for much of the tissue damage in capillaries

Type III

Delayed HS

Mediated by T_H cells and macrophages

Response peaks in days, not minutes