Type IV hypersensitivity

which type of sensitivity is the only one not antibody mediated

Type IV (T cell mediated)

delayed hypersensitivity reactions result from interactions among

antigen

APC

T cell

macrophage

why is type IV called delayed sensitivty

due to delayed appearance of response and symptoms

what does type IV hypersensitivity eliminate

intracellular pathogens

what is the clinical presentation of type IV reaction

induration (hard, raised lesions)

erythema and vesicles (reddened skin)

what is the tuberculin reaction

-Produced by intracutaneous injection of PPD (which is involved in TB)

-if previously exposed, delayed hypersensitivity response, swelling at injection site

lesions from tuberculin reaction are infiltrated with

mononuclear cells (lymphocytes, macrophages)

skin test can be used for

any infectious disease in which cell-mediated immunity has a significant role

what is allergic contact dermatitis

reactive chemical on skin triggers reaction by binding to PRRs, act as hapten carriers

what is the response during allergic contact dermatitis

skin macrophages present antigen to T cells in lymph node, T cells produce IFN-gamma and IL-17 --> activate CTL

what is the difference between atopic dermatitis and allergic contact dermatitis pathogenesis

AD= type I

ACD= type IV

what is the difference between atopic dermatitis and allergic contact dermatitis distribution

AD= face, nose, eyes, feet

ACD= hairless areas, ventral abdomen/ feet

what is the difference between atopic dermatitis and allergic contact dermatitis diagnosis

AD= immediate response

ACD= delayed response

T cell mediated hypersensitivity to drugs will lead to

rash that blisters into vesicles, develop skin ulcers

skin ulcers are formed due to

keratinocyte apoptosis, from drug binding to epidermal cells, triggering CD95L

what type of immune reaction occurs in type IV hypersensitivity

Th1 and CTL

what effector mechanism is used in type IV hypersensitivity

macrophage activation and cytotoxicity