Recent results suggest an activation of T-lymphocytes via the CD40L implying a dual function of this ligand involved in the activation of both B- and T-lymphocytes [1–4]. Here, we provide evidence that activation of T-lymphocytes via CD40L results in activation of a neutral but not an acidic sphingomyelinase correlating with a consumption of sphingomyelin and a release of ceramide. Activation of the neutral sphingomyelinase by the CD40L seems to involve a novel signalling cascade since it is independent of CD40L induced protein kinase activation or association of the neutral sphingomyelinase with the CD40L.
