A3 antibody B cells Flashcards
B cells and antibodies
key features of adaptive immune responses
specificity and diversity
-ensures response is targetted to relevent microbe
-can respond to variety of microbes
memory
-increased ability to combat infection by same microbe
clonal expression
-incrreases response to keep pace with microbe
specialisation
-generation of optimal type response
contraction and homoeostatis
-allows response to ‘reset’, no excessive inflammation
non reactivity to self
-prevents auntoimmunity
features of antibody
-variable region binds to specific antigen
-diff antibodies recognise/bind to different antigens or diff parts of antigens
-binding site is known as the epitope
-can be linear sequence or based on antigen folding
b cell generation
generated and selected in bone marrow
expresses b cell receptor BCR which recognises antigen
each BCR is different (adaptive)
recombination of genes similar to TCR
b cell variability
is associated with rearrangement of V-D-J regions of DNA
pre b cell randomly selects one of dozens of regions and links with other random units
generates variability within b cell population
-each b cell expressed different BCR
BCR structure and migration
structure is surface bound version of Ig
(when activated secretes antibody of same specificity)
once expressed functional BCR matures from bone marrow and enters periphery via lymph nodes
B cell activation
-recognition of antigen by bcr leads to activation of b cell and internalisation of antigen
-antigen broken down to peptides
-peptides loadedinto MHC II within b cell and presented to A.S CD4
-if t cell also recognises antigen it provides help (cytokines,costim)
-allows b cells to fully activate and secrete antibodies
b cell help
CD4 helper t cells help b cells via CD40
T cells influence antibody production through sytokines
induces proliferation of b cell and differentiation
-plasma cell
-memory cell
3 key functions of antibody
neutralisation
opsonisation
complement
