Unbalanced expression of Fas and CD40 in mantle cell lymphoma

B cells are characterized by the dual expression of CD40 and Fas receptors, which can mediate their survival and death, respectively. The balance between the dynamically opposing functions of these two receptors is important for B-cell selection, maturation and homeostasis. We found that mantle cell lymphoma (MCL) cells had a high level of CD40 and low or absent level of Fas, therefore favouring the CD40 cell survival pathway. Exogenous Fas ligand had no effect on MCL cells, whereas exogenous CD40 ligand enhanced their survival and rescued them from fludarabine-induced apoptosis. Our data raise the possibility that the prolonged survival of MCL cells in vivo may be explained by the unbalanced expression of Fas and CD40.