Adverse Immune Responses Flashcards
How do T cells become self tolerant to self antigens?
Not all are deleted in thymus Post thymic T cell tolerance- self reactive T cells abort self reactive T cells rendered anergic, deleted Maintained by immune regulation
How are self reactive B cells removed?
Removed in bone marrow and spleen
May abort, be deleted or anergized
Some may go into circulation
What causes autoimmunity?
Loss of self, non-self discrimination results in immune responses and damage to self tissue
What can induce autoimmunity?
Exposure of hidden antigens Formation of new epitopes Cross reactivity with microorganisms Induction by viruses Immunoregulation deficiency Histocompatibility antigen role
Name canine examples of autoimmune diseases?
Systemic lupus erythematosus
Rheumatoid arthritis
Name some organ specific autoimmune disease?
Muscle- myasthenia graves
Blood- autoimmune haemolytic anaemia
Anti-sperm antibodies
What is myasthenia gravis?
Auto antibodies are produced against Ach receptors so muscle cannot respond
Results in muscle wastage
What is a type 1 hypersensitivity?
Production of IgE to an antigen
Normally IgM switches to IgG/A for secondary response
Gene deletion can lead to IgE to be produced instead
Hate fever, astma
What is a type 2 hypersensitivity?
Antibodies (self antibodies) bind to antigens on host tissues or cells
Tissue damage caused by ‘frustrated’ phagocytes and complement activation caused
Haemolytic disease in new born foals
Canine haemolytic anaemia
What is type 3 hypersensitivity?
Immune complexes form or deposit on host tissues
Excess antibodies activates complement or trigger PMNs to release destructive enzymes
Glomerulonephritis
What is a type 4 hypersensitivity?
T cell mediated-
Primed T cells responds to chronic antigen load by production of cytokines which attract and activate macrophages and these damage tissues by release of proteolytic enzymes and other mediators
TB testing in cattle
Why are skin grafts rejected?
Rejection of foreign tissues, mainly caused by differences in MHC I and II between host and donor
Therefore recognised as foreign by host, mediated by cytotoxic T cells and macrophages
