Immunology Chapter 16 — Disruption of healthy tissue by the
adaptive immune response
Autoimmune diseases – immune response against “self”
More than 100 different types
More common in industrialized countries
Higher incidence in females than males
Chronic disease – you cannot be cured
Failure to achieve tolerance (inhibition) for self. What causes these failures?
This is not exactly known. One of the hypotheses is the hygiene hypothesis:
countries low incidence of infectious diseases due to high hygiene have high
incidence of autoimmune diseases
Often runs in the families – genetic predisposition is mainly mediated by HLA
molecules. For certain autoimmune diseases there is a correlation with MHCI
allotypes but the correlation with MHCII allotypes is much stronger.
So, this suggest that there is a relationship between T helper cell activation
and autoimmune diseases
Mechanism to achieve tolerance (inhibition) for self
Central tolerance: induced in primary lymphoid organs
o Thymus – T cells
Apoptosis
Regulatory T cells are induced: suppress the CD4+ T cells
o Bone marrow – B cells
Receptor editing
Apoptosis
Anergy
Peripheral tolerance
o Apoptosis
o Anergy
o Regulatory T cells: suppress the CD4+ T cells
Different types of autoimmune disease
Antibody mediated
1. Antibodies directed against cell surface or matrix antigens (type II)
a. Autoimmune haemolytic anemia
Patients make antibodies against red blood cells --> antibodies bind to
red blood cells --> complement is activated and there is direct lysis of
red blood cells + red blood cells are being cleared because they bind to
FcR expressed on macrophages in the spleen this led to phagocytosis
Consequence: destruction of red blood cells by complement and
phagocytosis which lead to anemia (lack of healthy red blood cells)
Symptoms: fatigue, weakness, irregular heartbeats, shortness of
breath, dizziness
Cause: unknown but it can be drug induced by penicillin. Penicillin can
bind to surface of red blood cells and acts as an antigen and this raises
the antibodies
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