B cell activation, hypermutation and class switching Flashcards
in the bone marrow
progenitor B cells produce a precursor B cell by somatic mutation of the heavy chain
precursor B cell produces
an immature B cell via somatic mutation of light chain (IgM)
immature B cell (IgM) migrates to the
lymph nodes via efferent lymphatic system
in the lymph nodes B cells producing
become maturee in the lymph nodes, expressing IgM and IgD
B cell activated by
T helper cell or antigen of a pathogen or dendritic cell
after B cell activation by T helper cell or antigen
B cell moves into the germinal centre and begin to proliferate via clonal expansion
what introduces point mutations into variable regions of the DNA that code for variable antibody
AID
AID is an
intracellular enzyme which introduces point mutations in the variable regions of DNA that codes for variable regions of the antibody—> introducing mutations (hypermutation)
hypermutation to the DNA encoding variable regions of the antibody causes
either an increase or decrease in antibody affinity to specific antigen
hypermutation produces
many types of B cells which produce antibodies with either ran increased affinity or decreased affinity for antigen
B cells then present their antibodies to
T helper cells which still carries the antigen originally presented to the B cell
B cells with disadvantageous mutations
have a lower affinity for antigen…. are destroyed via apoptosis
B cells with mutation which have increased affinity of antibody undego
class switching and differentiation
B cells with increased affinity undergo differentiation into
plasma cells or memory B cells
hypermutation via point mutations (AID) leads to
changes in variable regions –> changes to CDRs… leading to increased or decreased affinity
