This upregulation of CXCR4 might be due to CD40L induced downregulation of EBNA-2 and LMP-1.[51] Similar to CLL cells, slight upregulation of IL-21R and downregulation of CD38 was noted in MEC2 cells in response to CD40L.[48] CD40L induced no significant change in IL-21R and CD38 expression in MEC1. Here, CXCR4 is linked to B-cell chronic lymphocytic leukemia.