hypersensitivity continued Flashcards
What is the mechanism of Type III hypersensitivity?
Immune complexes (antigen-antibody complexes, mostly IgG) activate complement, attracting neutrophils, which release lysosomal enzymes → inflammation and tissue damage.
What are examples of Type III hypersensitivity?
Systemic lupus erythematosus (SLE).
Rheumatoid arthritis.
Reactive arthritis.
Polyarteritis nodosa.
Poststreptococcal glomerulonephritis.
IgA vasculitis.
What is serum sickness in Type III hypersensitivity?
A prototypic immune complex disease caused by antibodies forming complexes with foreign proteins, which are deposited in tissues (1–2 weeks after exposure) → complement activation → inflammation and tissue damage (↓ serum C3, C4).
What are symptoms of serum sickness?
Fever, urticaria, arthralgia, proteinuria, and lymphadenopathy 1–2 weeks after antigen exposure.
What is an Arthus reaction in Type III hypersensitivity?
A local subacute immune complex-mediated reaction caused by intradermal antigen injection into a presensitized individual, leading to immune complex formation in the skin → edema, fibrinoid necrosis, complement activation.
What is the mechanism of Type IV hypersensitivity?
Direct cytotoxicity: CD8+ T cells kill target cells.
Inflammatory reaction: Effector CD4+ T cells release cytokines, activating macrophages and inducing inflammation.
What distinguishes Type IV hypersensitivity from other types?
It is T cell-mediated and does not involve antibodies.
involvves mmory t cells
What are examples of Type IV hypersensitivity?
Contact dermatitis (e.g., poison ivy, nickel allergy).
Drug reaction with eosinophilia and systemic symptoms (DRESS).
Graft-versus-host disease.
What are tests for Type IV hypersensitivity?
PPD test for TB infection.
Patch test for contact dermatitis.
Candida skin test for T cell immune function.
What are the ‘4 T’s’ of Type IV hypersensitivity?
T cells.
Transplant reactions.
TB skin tests.
Touching (contact dermatitis).
what is a classic example associated with serum sickness ?
where a patient has been administered antitoxins a hapten or monoclonal antibodies , then a wk or 2 later the triad of arthalgia fever and rash appear
how can arthus reaction b detected ?
by immunofluoresnnecce
what is the classic scenario in association with arthus reaction ?
someone who has taken a booster vaccine
repetitive insulin injection
hyperssens pneeumoonitis ( farmers lungs )
what type of hypersensitivity is associated with MS ?
type 4
what are thee compliment levels like in serum sickness ?
low 3 and c4
