Role of Th cells in heavy chain isotype switching by activated B cells.

Cytokines produced by Tfh cells determine what type of antibodies will be produced. Secreted cytokines depend on Th cell type (Th1, Th2 etc). Activated helper T cells that express CXCR5 that direct migration to adjacent follicles They become follicular T cells (Tfh) ,Some B cells are coming back and rapidly dividing (6h doubling time) in response to Tfh to form germinal center where mutations and isotype switching takes place