HUMAN CD38 IS ASSOCIATED TO DISTINCT MOLECULES WHICH MEDIATE TRANSMEMBRANE SIGNALING IN DIFFERENT LINEAGES

The CD38 antigen displays restricted functional associations with surf ace molecules involved in immune system and complement. Capping of the CD38 molecule in normal or neoplastic T cells is followed by rapid an d specific co-modulation of the CD3-T cell receptor (TcR) complex. In normal and tumor cells of B lineage, CD38 was found to be also associa ted with surface Ig (sIg) and with the complement receptor 2 (CR2)/CD1 9 complex. The CD38 molecule expressed by purified natural killer cell s displayed an association with the low affinity IgG Fc receptor (Fcga mmaRIII) CD16. These observations suggest that specialized areas in th e plasma membrane contain co-modulating structures, including differen t receptors involved in the transduction of extracellular signals. We propose a model whereby TcR, CR2 and CD16 are ligand binding structure s in their respective lineages, while CD38 is a molecule involved in t he intracellular transduction of the signals.