Autoimmnity Flashcards
What is autoimmunity
the presence of immune responses against self antigens
what can cause chronic inflammation
high titres of auto-antibodies or auto-reactive T cells
When is there a large potential for the development of auto reactive B/T cells
during normal lymphocyte development in primary lymphoid tissues
Which part of the Ig gene locus decides the class of antibody
constant region
Which variable gene segments does the heavy chain have
D
V
J
Which variable gene segments does the light chain have
V
J
What stage of the B cell is the chain sequences transcribed
progenitor B cell
What gives the variable region of the B antibody its specificity
1 gene segment at random is selected from D, V and J giving it a unique peptide sequence when translated
What happens to the gene segments not selected
are cut out, leaving only the 3 selected genes next to each other
How are auto-reactive T cells tested for that could respond to self antigens
receptors are tested in thymus against self antigens from across the body
when are progenitor B cells allowed to reach maturation?
if they do no have a strong reaction to self antigens during the “training phase”
How are immune cells with self-antigen receptors which reach maturation inactivated
regulatory T cells
How can genetics cause autoimmunity
single gene defects
complex genetic overlaps
genes expressed for HLAs
what is a common overlap of genes that causes autoimmune disease
HLA genes
What are MHC molecules also referred to
HLA (human leucocyte antigen)
Can a sigle mhc1/mhc2 molecule present different peptides
yes
How do HLAs cause autoimmunity
some genetic codes for HLAs produce HLA proteins with more affinity for self-antigens
what environmental factors influence autoimmune disease in people with genetic predispositions
smoking
infection
hormone levels
tissue damage
what molecular mechanisms can cause autoimmunity from the environment
alteration to self antigens
bacterial superantigens
antigen sequestration
what does alteration to self antigens cause
self-antigens become immunogenic if altered chemically
how does antigen sequestration occur
self antigens normally ‘hidden’ from body are produced in result to damage and are unrecognised by body immune cells
What is a bacterial super antigen
toxic shock
toxins from bacteria are super-antigens
activate T cell receptor without secondary signal
