When Do Isotypes Matter? The primary -> secondary immune response: Increase Ig titer Switch from IgM to IgG Increase Ag binding affinity
Where and when do affinity maturations and isotype class switch occur?? BCR:mIgM sIgGmIgG CSR/SHM
Infection and Ag presentation
T cell zone B cell zone Red pulp border Generation of plasmablasts in the spleen
T cells: CD4+ and CD8+ CD8+ CD4+
APCs: present Ag in the context of MHC class II to T helper cells
Ag presentation to T helper cells in the spleen
T helper cells are CD4+ are activated by APCare activated by APC secrete cytokines tosecrete cytokines to augment the immune response
T helper cells polarize into T H 1 and T H 2 cells into T H 1 and T H 2 cells and secrete unique and secrete unique combinations of combinations ofcytokines
Cytokines target germline transcripts to specific Ig isotypes in B cells
Cytokines target germline transcripts to specific isotypes 3333 2b 2b
T cell zone B cell zone Red pulp border Germinal Center
SHM Occurs in the Germinal Center B Cells
Primary focus SHM Occurs in Germinal Center B Cells
T cell zone Red pulp border Germinal Center Primary focus plasmablasts T cell zone
sIgM sIgM and sIgG