Autoimmunity Flashcards
what is autoimmunity
exaggerated immune response to self-antigens/tissues the body has lost tolerance to self-antigens
how does tissue damage happen in autoimmunity
autoreactive T cells or antibodies cause tissue damage through hypersensitivity reactions
what is immunological tolerance
unresponsiveness to an antigen as a result of previous exposure to that antigen
what is a tolerogen
an antigen that induces tolerance
what is the role of the thymus
eliminates T cells with a high affinity for self antigens or no affinity for antigens at all (positive and negative selection)
what happens to T cell that are unreactive to antigens in the thymus
death by neglect
what happens if a mature lymphocyte in circulation recognises a self-antigen
they become incapable of activation and die by apoptosis they have anergy and treg suppression to prevent them from attacking self-antigens
how can peripheral tolerance be overcome
inappropriate access or self antigens or inappropriate/increased expression of co-stimulatory moleculesor alterations in the way self molecules are presented
what can increase the risk of overcoming peripheral tolerance
tissue damage/inflammation because the proteolytic enzymes cause high concentrations of peptides getting presented to T cells
what do B1 cells produce
natural antibodies
where are B1 cells
in the lining of the gut
what is the role of B1 cells
produce natural antibodies against gut bacterianatural antibodies bind to a range of antigens at low affinity
what can the natural antibodies bind to
supposed to bind to gut bacteria with low affinity can also bind to -nuclear proteins and DNA from apoptotic cells -A or B antigens on RBCs
what is molecular mimicry
structural similarities between self proteins and microbes can cause an autoimmune response
how can T cell tolerance decline
- fewer autoreactive cells deleted - DNA can leak out of dying cells and not be cleared - physical barriers around cells can become defective - molecular mimicry
