Immune mediated disorders" Hypersensitivity

Question 1

What is a hypersensitivity d/o?

Answer 1

immune response to exogenous and endogenous antigens (Ag)=. inflammation and tissue damage

Question 2

what are the 4 types of hypersensitivity responses?

Answer 2

1. T1 is IgE- mediated; allergy, asthma
2. T2 is ab mediated: miss matched transfusion, graft rejection
3. T3: due to Ag-Ab complexes: vasculitis
4. T4 is cell mediated immune response : CTL, CTH

Question 3

What is Type 1 hypersensitivity?

Answer 3

IT1HS= a rapid IgE and mast cell mediated vascular and smooth muscle response that occurs in gen susceptible ppl.
This type of reaction results from excessive Th-2 responses, we know these RE’s as allergies

Question 4

What hypersensitivity disorder type responds to Ag ( allergen): protein from dust, chemical, animal hair, food, pollens

Answer 4

type 1

Question 5

What does T1 HS triggers in response to allergens?

Answer 5

a local or atopic reaction that can go from mild (rhinitis) to debilitating 9asthmas) to life threatening (anaphylaxis)

Question 6

What results in Antibody mediated type 2 reactions?

Answer 6

when antibodies are directed against antigens on the surface of cells or other tissue components. The deposition of the antibody can have variety of detrimental efffects incl inflammation, opsonisation and phagocytosis or functional derangements.

Question 7

Type 2; antibody mediated D/O

C’- and Ab mediated cell destriction

Answer 7

eg. mismatched blood transfusion reactions, haemolytic of the newborn due to ABO or Rh incompatibility
1. . via C’ : cells are opsonised by molecules that attract phagocytes or are destroyed by the formation of the MAC
2. via ADCC= Ab- dependant cell- mediated cytotoxicity. cels are covered with IgH Abs and are killed by effector cells binding through their receptors for IgG. Cll lysis occurs without phagocytosis.

Question 8

Type 2 antibody mediated disorders:

C’ and b -mediated inflamation

Answer 8

e. g glomerulo nephritis, vascular rjection of organ grafts
1. Abs deposited in extracellular matrix=> inflamm reaction. attraction of neutrophils=> rlls of reactive oxygen species and enzymes

Question 9

T2, antibody mediated DO:

Ab-mediated cellular dysfunciton

Answer 9

eg. graves disease: auto Ab against thyrpis stimularing hormone (TSG) receptors on thyroid cells stimulate thyroxine production=? hyperthyroidism:
1. Ab binding to specific target cells does not lead to cell death but change in function

Question 10

what results in immune complex mediated (T3) HS?

Answer 10

when complexes of antibodies and antigens deposit in vascular walls or other tissues and cause inflame response. this type of pathology is commonly implicated in vasculitis and arthritis

Question 11

describe T3 immune complex mediated DOs

Answer 11

1. complexes=> damage when contact w. vessel lining or are deposited in tissue (renal glomerulus, skin venues, lung tissue, joint synovium)
2. once deposited=> inflame response (C’)=> neutrophils infiltration + inflammatory cells + inflammatory mediators => tissue damage

e.g vasculitis in some autoimmune disease such as stem lupus erythematosus (SLE)