Follicular helper T lymphocytes in health and disease

Figure 1 Follicular helper T cells and the differentiation program of B lymphocytes. A: Naïve CD4⁺ T cells are activated following recognition of antigen (Ag) presented by dendritic cells (DC) in T cell zones. Upon antigen activation and co-stimulation by DC, nascent T_FH upregulate CXC-chemokine receptor 5 (CXCR5), downregulate CC-chemokine receptor 7 (CCR7) and migrate towards B cell follicles; B: At the T-B border TFH contact antigen-activated B cells that move to the T-cell zone after upregulating CCR7. T_FH deliver help to B cells resulting in their differentiation into short-lived extrafollicular plasmablasts or their migration into B cell-follicles to form germinal centers (GCs); C: Within GC, T_FH promotes the B cell differentiation into long-lived plasma cells and memory B cells. T_FH: Follicular helper T lymphocytes; FDC: Follicle dendritic cell; BCR: B cell receptor; MHC: Major histocompatibility complex; TCR: T cell receptor.