hypersensitivity and autoimmunity

Question 1

define organ specific autoimmune disease

Answer 1

one in which an immune response is directed toward antigens in a single organ

e. g. thyroid: Hashimoto’s thyroiditis, primary myxoedema, thryotoxicosis
stomach: pernicious anaemia
adrenal: Addison’s disease

Question 2

define non-organ specific autoimmune disease

Answer 2

autoimmune activity is widely spread throughout the body

e. g. muscles: dermatomyositis
skin: scleroderma
kidneys: SLE
joints: rheumatoid arthritis

Question 3

what is loss of tolerance due to in AI disease

Answer 3

abnormal selection or lack of control of self-reactive lymphocytes

Question 4

hypersensitivity responses

Answer 4

hyper response from the immune system that is harmful and may cause tissue injury or serious disease
I, II, III (V) - antibody mediated
IV - T cell mediated
autoimmune diseases usually fall into II, III and IV depending on the damage associated with the disease

Question 5

type I antibodies

Answer 5

IgE - soluble antigen

allergy

Question 6

type II antibodies

Answer 6

IgG - cell matrix or antigen

rheumatic fever

Question 7

type III antibodies

Answer 7

IgG - soluble antigen

rheumatoid arthritis

Question 8

type IV cells

Answer 8

Th1 - soluble antigen
Th2 - soluble antigen
CTL - cell antigen
type I diabetes

Question 9

type I hypersensitivity

Answer 9

allergen is taken up and presented by a dendritic cell to a naive T cell
drives B cell response
IgE produced and binds to Fc receptor
allergen cross links the antibody and activates the mast cell
pro-inflammatory mediator (propagate the inflammatory response) and cytokines are generated very quickly

Question 10

early phase response in allergy

Answer 10

IgE mediated effects
vasodilation, oedema, vascular congestion
occurs within minutes
preformed mast cell mediators

Question 11

late phase reaction in allergy

Answer 11

newly synthesised mediators (prostaglandins, leukotrienes)
Th2 cytokines
eosinophil mediators

Question 12

atopy

Answer 12

predisposition to allergy
depends on IgE levels
high = likely to develop at least one allergy

Question 13

type II hypersensitivity

Answer 13

body’s antibodies bind to antigens on its own cell surfaces
antibodies are produced in response to the antigens on the cell surfaces
IgG and IgM antibodies trigger the complement system causing cell lysis

Question 14

type III hypersensitivity

Answer 14

characteristed by the formation of immune complexes (clumps of antibodies that have stuck together)
low conc of antibody coupled with a large conc of antigen causes small complexes to form

Question 15

type IV hypersensitivity reactions

Answer 15

A) cytokine mediated: APC presents fragments of protein to CD4 T helper cells, recognise the foreign antigen and produce cytokines which drives pro-inflammatory responses, leading to tissue injury
B) T cell mediated: T cells recognise antigens demonstratedy by normal epithelial cells, leading to tissue injury

Question 16

type V hypersensitivity reactions

Answer 16

stimulate the receptor, inappropriate increase in function response e.g. myasthenia gravis - Ach cant bind to receptor on muscle, loss of muscle function

Question 17

define the pathophysiology of immune complex formation in localised type III hypersensitivity

Answer 17

causes localised inflammation and can be cleared away by macrophages

Question 18

define the pathophysiology of immune complex formation in systemic type III hypersensitivity

Answer 18

complexes are deposited in tissues and organs such as the skin, joints, kidneys and blood vessels

Question 19

define the term autoimmune disease

Answer 19

a large group of clinical disorders characterised by tissue or organ damage mediated by incorrect immune mechanisms targeted at self antigens

Question 20

illustrate the factors involved in the aetiology of AI disease

Answer 20

caused by interaction of: genetics, immune regulatory factors, hormonal, environmental and ‘other’ factors

Question 21

describe the pathogenic mechanisms involved in AI disease

Answer 21

cell mediated
antibody mediated
antibody and complement 
immune complex mediate
recruitment of innate compounds

Question 22

Fc receptors

Answer 22

antibody receptor involved in antigen recognition which is located at the membrane of certain immune cells including B lymphocytes, natural killer cells, macrophages, neutrophils, and mast cells. Such receptors recognize Fc fragment of antibodies

Question 23

immune tolerance

Answer 23

Tolerance is the prevention of an immune response against a particular antigen.

Question 24

how does immunological tolerance develop

Answer 24

T cells, possessing receptors which strongly bind onto one of the body’s own peptides bound to an endogenous MHC molecule, are triggered to undergo apoptosis