hypersensitivity and autoimmunity week 5 Flashcards
who has the potential to develop an autoimmune disease
everyone
what are hypersensitivity responses
harmful immune response that may produce tissue injury and cause serious disease
- 4 categories: I, II, III, IV, (V)
what antibodies are associated with type I
IgE
- allergy
what antibodies are associated with type II and III
IgG
what cells are associated with type IV
T helper 1/17
T helper 2
CTL- cytotoxic T cell
what happens in type I
- first exposure to antigen
- activation of T follicular helper cells (IL-4 producing) and stimulation of IgE class switching in B cells
- production of IgE
- binding of IgE to FcRI receptor on mast cells
- repeated exposure to allergen
- activation of mast cell, release of mediators
- mediators: vasoactive amines, lipid mediators (immediate hypersensitivity reaction after repeat exposure) and cytokines (late phase reaction, 2-4 hours after repeat exposure)
what are the effects of type I
mast cell: vasodilation, vascular leak, broncho-constriction, intestinal hyper motility, inflammation, tissue damage
eosinophil: killing of parasites and host cells, tissue damage
what happens in immediate phase of type I
- IgE mediated effects
- vasodilation, oedema and vascular congestion
what happens in the late reaction of type I
eosinophil, neutrophil and T cell infiltrates
what is atopy
predisposition to allergy
associated with high levels of IgE
what is type II
injury caused by anti-tissue antibody
- antibody deposition in extracellular matrix, they can interact via Fc gamma receptor (reacts with IgG)
- this leads to mediated recruitment and activation of inflammatory cells such as neutrophils and macrophages
- these cells start releasing lysosomal enzymes and reactive oxygen species which will generate tissue injury and pro-inflammatory response
what is type III
immune complex-mediated tissue injury
- circulating immune complexes (can contain thousands of antibodies)
- complement and Fc receptors result in mediated recruitment and activation of inflammatory cells (neutrophils release lysosomal enzymes, reactive oxygen species)
- this results in vasculitis if site of deposition in blood vessel
what response is possibly type II and V
abnormal physiological responses without cell/tissue injury
- antibody stimulates receptor without ligand
- antibody inhibits binding of ligand to receptor
what is type IV
2 types:
cytokine-mediated inflammation
- CD4+ on T cell bound to tissue antigen on macrophage
- CD8+ on T cell is bound to receptor on tissue
- both of these T cells release cytokines which results in inflammation and tissue injury
T cell-mediated cytotoxicity
- CD8+ bound to receptors on tissue
- this results in cell killing and injury
what is immune tolerance
- state of unresponsiveness to specific antigen
- antigens can be self or foreign
- prevents adaptive responses that are damaging
- can be exploited by microbes and tumours
what is a systemic autoimmune disease
- autoimmune process is spread throughout the body
- affects more than one organ (not necessarily the same ones in different individuals)
what is organ specific autoimmune disease
- autoimmune process directed against one organ
- e.g type 1 diabetes or autoimmune thyroiditis
what is an autoimmune disease
a failure or breakdown of immune system that maintains tolerance to self tissues
what is loss of tolerance is autoimmune diseases probably due to
probably due to abnormal selection or lack of control of self-reactive lymphocytes (b and T cells)
what can lead to autoimmune disease
chronic activation
what is lupus
a systemic autoimmune disease
how do they treat autoimmune disease
- typically blanket immunosuppression
