PATHOLOGY

Detailed explanation-1: -CD40 signaling of B cells promotes germinal center (GC) formation, immunoglobulin (Ig) isotype switching, somatic hypermutation (SHM) of the Ig to enhance affinity for antigen, and finally the formation of long-lived plasma cells and memory B cells (14).

Detailed explanation-2: -CD40 and CD40L are both reciprocally expressed on activated DCs and lymphocytes, and may engage in multi-directional crosstalk between cell types. CD40 signaling on DCs induces secretion of secrete IL-12 which promotes Th1 differentiation, IL-10 that induces Tregs or other cytokines that induces Th17 differentiation.

Detailed explanation-3: -Coupling of this newly expressed CD40L on T cells with CD40 on APC results in expression of the costimulatory activity of the APC. At this time the costimulatory signal provided by the APC is received by the T cells via CD28/CTLA-4, which drives the cell to enter into cell cycle and complete T cell activation.

Detailed explanation-4: -CD40L/CD40 interaction in cellular immunity Among a multitude of cellular functions, CD40L regulates the costimulatory activity of APCs, inducing B cells to upregulate the expression of CD80 (B7. 1) and CD86 (B7. 2) and DCs to upregulate the expression of CD54 and CD86.