adaptive immunity (basics) (W11) Flashcards
name for lymphocyte is its never been activated
naïve lymphocyte
what occurs to a lymphocyte after it binds to their specific antigen
activated and differentiate into effector cells - either T cells or effector B cells
also differentiate into memory T/B cells
B cells function?
produce antibodies
what occurs to B cells once activated
become plasma cells (aka effector B cells)
variable region on antibody?
antigen binding site, varies between antibodies
T cells that kill virally infected cells?
CD8+ Cytotoxic T lymphocyte (CTL)
T cells which organise immune responses by producing different cytokines
CD4+ T helper cell (Th cell)
first thing that occurs after a T/B cell binds to its specific antigen
proliferates
some daughter cells go on to become memory cells
generation of BcR/TcR diversity - random
variable regions encoded by variable, diversity and joining gene segments (V,D,J).
gene must be rearranged (somatic recombination, DNA chopped out).
many different variable regions on one B cell receptor.
random mix of V D and J.
name for specific binding site of an antigen
epitope
2 classes of MHC and what they bind to
CD8+ CTLs bind antigen on class 1 MHC
CD4+ T helper cells bind antigen on class 2 MHC
where is class 1 MHC present? why?
on the surface of all nucleated cells
presents endogenous proteins of that cell on the cell surface
where is class 2 MHC present? which of these are the most important?
specialised antigen presenting cells (APC)
most important of which are dendritic cells
function of class 2 MHC?
present exogenous antigens
structure of class 1 MHC?
alpha chain (made of 3 domains) bound to beta-2 macroglobulin
alpha 1 and 2 domains make up peptide-binding cleft
structure of class 2 MHC?
alpha and beta chain
(2 alpha domains, 2 beta domains)
alpha 1 and beta 1 domain make up peptide-binding cleft
why is diversity in MHC required
increases the diversity of antigens presented to T cells
what part of MHC do peptides bind to?
anchor pockets (vis anchor amino acids)
what do anchor pockets react with?
only a limited range of biochemically similar ‘anchor’ amino acids on peptides
strategies to overcome the limited range of anchor pocket reactions
polygeny - multiple independent genes for each MHC type
co-expression - alleles inherited from mother and father
polymorphisms - multiple variants of each gene within the human population
why is polymorphism important in regards to viruses
viruses evolve to edit out certain amino acid sequences from there viral genome, polymorphism stops this by presenting as many different peptides as possible
MHC in transplant rejection?
very rare for 2 unrelated individuals to express the same combination of MHC variants - transplant seen as non self
prevention of unnecessary and harmful responses to self and environmental antigents?
immunological tolerance
2 types of immunological tolerance
central and peripheral tolerance
