Lecture 10

Question 1

For Type 2= ab mediated cytotoxic hypersensitivity list the main players,

Answer 1

Type 2= ab- mediated cytotoxic hypersensitivity
main players 1gG (IgM), complement, macrophages
(phagocytosis) NK cells
mode of action; ab reacts with surface of normal cell, normal cells are then destroyed by complement or cytotoxic cells
there is lysis of cell- rapid
lesions may results from destruction of cells- delayed

Question 2

Give an example of a type 2 hypersensitivity reaction

Answer 2

example of a type 2 hypersensitivity reaction
blood transfusion
RBCs have surface ag for example if you have blood type B you will have ab for type O and A
reactions to incompatible transfusion include;
blood clotting
can be fatal
potassium is released from lysed RBC

Question 3

For the following blood types list the surface antigen and antibodies 
type A
type B
type AB
type O

Answer 3

-Type A; 
surface ag; A
anti-B antibodies
-Type B;
surface ag; B
anti-A antibodies 
-Type AB; 
surface antigen A and B 
neither anti A nor anti B antibodies 
-Type O
either A nor B surface antigens 
Anti-A and anti-B antibodies

Question 4

Explain type 3 - immune complex hypersensitivity

Answer 4

Type 3- Immune complex hypersensitivity
ag ab complexes form immune complexes activated the complement
its localised or systemic
phagocytic cells are recruited
phagocytic cells release oxidants and other enzymes causing acute inflammation and tissue damage

Question 5

What is an example of a type 3 hypersensitivity reaction

Answer 5

example of a type 3 hypersensitivity reaction
Arthus reactions
immune complex are deposited at site of Ag penetration.
localised lung inflammation reaction
can be associated with vaccinations
local vasculitis due ti deposition of immune complexes in dermal blood vessels, chemotactic, inflammation.

Question 6

Explain Type 4 delayed type hypersensitivity reaction

Answer 6

Type 4- delayed type hypersensitivity
type 4 is cell mediated
sensation phase generates Th1 cells and ag specific memory T cells , this leads to reactivation of these memory cells
these cells release IFN gamma and other cytokines and chemokines.
example is a DTH reaction contact dermatitis

Question 7

Give an example of Type 4 delayed type hypersensitivity reaction

Answer 7

example of Type 4 delayed type hypersensitivity reaction
example is a DTH reaction contact dermatitis
soluble molecules called happens penetrate skin and attach to protein of epidermis,
recognised as forge in by skin langerhan cells , transport modified skin proteins to lymph nodes to prime and activate T cells
the main players are cytokines and T cells

Question 8

For type 1 hypersensitivity list 
main isotope 
mechanism 
what it causes 
its time of action 
what mediates it

Answer 8

type 1 hypersensitivity
IgE mediated
IgE is bound to mast cells an ag binds to these ab, cross linking of IgE induces degranulation
causes localised and systemic anaphylaxis, seasonal allergies like hay fever
immediate
mediated by igE and mast cells

Question 9

For Type 2 hypersensitivity list definition
mechanism
how it relates to mismatched blood transfusions

Answer 9

Type 2 hypersensitivity
IgG mediated cytotoxic hypersensitivity
cells are destroyed by bound ab by activation of complement or cytotoxic T cell with Fc receptor for ab
RBC destroyed by complement and ab during tranfusion of mismatched blood type

Question 10

For Type 3 hypersensitivity list the definition
mechanism
common forms

Answer 10

Type 3 hypersensitivity
immune complex mediated hypersensitivity
ag-ab complexed are deposited in tissues cause the activation of complement, which attracts neutrophils to the site
most common forms of immune complex disease are seen in glomerulonephritis

Question 11

For Type 4 hypersensitivity list the definition
mechanism
common form

Answer 11

Type 4 hypersensitivity
cell mediated hypersensitivity
Th1 cells secrete cytokines which activate macrophages and cytotoxic T cells and can cause macrophage accumulation at the site
most common forms are contact dermatitis