Immunology Flashcards
What will cause autoimmune diseases?
High titres of auto-antibodies and/ or auto-reactive T cells
This leads to significant tissue/ organ damage and chronic inflammation
What is the pathogenesis of autoimmune diseases?
Genetic susceptibility
Breakdown of self-tolerance and loss of immune regulation
Activation of auto-reactive T and B cells
Hypersensitivity reactions
Autoimmune phenomena and autoimmune disease
What is immunological tolerance?
Process by which the immune system recognizes and accepts self-tissue
How does self-tolerance restrain auto-reactive lymphocytes?
Immature self-reactive lymphocytes are killed as they develop in primary lymphoid tissues
Activity of any mature self-reactive lymphocytes that escape this killing process are suppressed by specialised Tregs in peripheral tissues
What does the FOXP3 gene code for?
Essential for the development of CD4+ regulatory T cells
What is IPEX syndrome?
Mutation in FOXP3 gene leads to severe infections, intractable diarrhoea, eczema, diabetes mellitus
What is the function of MHC molecules?
T cells require proteins to be procesed and peptides derived from these to be presented to their T cell antigen receptor by MHC molecules
What MHC molecule do all nucleated cells express?
Class 1 molecules
What cells express class 2 MHC molecules?
Sepcalised antigen-presenting cells
What chomosome expresses HLA/ MHC molecules?
Chromosome 6
How does sex influence autoimmune diseases?
Different hormonal influences on lympmhocyte function in males and females
Alteration of couse of some autoimmune diseases during pregnancy
What environmental factors influence autoimmune diseases?
Molecular mimicry
Intercurrent infections
Tissue damage
Superantigens
What is molecular mimicry?
T and B cells with cross-reactive antigen-receptors are activated by non-self peptides that resemble or are identical to endogenous peptides (rheumatic fever after streptococcal infection, halothane hepatitis)
What is antigen sequestration?
Some self-antigens are hidden from the immune system because the tissues in which they are present do not comminucate with blood or lymph
Developing T and B cells whose antigen-receptors recognise these self-antigens are not deleted
Any tissue damage that releases these hidden antigens results in activation of auto-reactive T and B cells
Where can hidden antigens be found?
Testis
Eye
Brain (BBB)
What is a bacterial superantigen?
Can activate T cells non-specifically without proper antigen presentation