FAS and Burkitt lymphoma: As in normal GC B-lymphocytes, CD40 rescues apoptosis induced by Fas in low-grade B lymphoma, but CD40 sensitizes Burkitt lymphoma B cells to Fas-induced apoptosis.42, 43, 44 In a similar way, CD40 triggering protects Burkitt lymphoma13 and follicular lymphoma,45, 46 but sensitizes chronic lymphocytic leukaemia B cells to apoptosis induced by TRAIL.47 The measure of TRAILR2 expression revealed that expression of this receptor is increased in marginal zone compared with switched memory B cells and that this difference is maintained upon CD40L+IL-21 stimulation.