L2 Immune recognition Flashcards
what are the two types of recognition molecules
B cells (B cell receptor/immunoglobulin) T cells (TCR)
what is the B cell immunoglobulin structure
2 heavy 2 light chains, constant and variable domains at the two combining site - antigen binding
Hinge
how come B cell immunoglobulins move to bind to target
have a hinge
what is the T cell receptor structure
Alpha and beta chain has constant (close to cell surface) and variable domain – only one antigen combining site made of variable alpha and beta chain
what is the difference between B and T cell recognition
T cell cant directly recognise need info presented to them via antigen presenting cell
how do B cells recognise
surface Ig – bind directly to pathogen /antigen
what happens to B cell following recognition
B cell activated makes plasma cells = lots more Ig which all bind to the pathogen
how do T cells recognise
needs info of pathogen processed and presented to it via MHC
antigen presenting cells do this e.g. dendritic cells
what happens to T cell following recognition
effector cell activated – might be CD4 or CD8 (depends on the MHC)
where is there variability the variable domains
areas of hypervariability – variation between amino acid structure is huge = will recognise a different target
3 areas of hypervariability in heavy and light
how are B cells activated
only through B cell clustering
Ig alpha and Ig beta have capacity to signal to cell to become activated – have tyrosine receptor molecules to intracellulary activate Ig alpha and beta molecules found in conjunction with B cell receptor
why cant the B cell become activated by itself
might be a chance encounter with antigen or might bind to a target not specifically – can’t have this or adaptive response and B cells constantly activated
what does BCR complex clustering cause
lots of B cells bind to target = B cell receptor clustering
turns on Ig alpha and beta signal B cell to start making lots of antibodies
what is the BCR co-receptor complex
second signal through complement receptors binding to complement that has opsonized the pathogen
what is needed for B cell to make antibodies
BCR clustering and BCR co-receptor complex
what is the TCR for
not able to signal only there for indirect recognition via antigen presenting cell
what are the two classes of TCR
alpha beta
gamma delta
what are the T cell co-receptors
CD$
CD8