INDUCTION OF NK-LIKE ACTIVITY IN T-CELLS BY IL-2 ANTI-CD3 IS LINKED TO EXPRESSION OF A NEW ANTITUMOR RECEPTOR WITH SPECIFICITY FOR ACETYLATED MANNOSE

The generation of MHC-unrestricted cytotoxicity of highly enriched hum an CD3+ T cells (95-99%) by treatment with IL-2 and/or anti-CD3 antibo dies was studied T cells obtained by positive immunomagnetic sorting ( anti-CD3) developed comparable specific cytotoxicities against K562 an d Daudi cells when cultured with IL-2 and anti CD3 for 96 h (80% of do nors; n=25). This increase of MHC-unrestricted cytotoxicity correlated fairly well with an increased formation of T cell/tumour cell conjuga tes. Moreover, simultaneous expression of a rhamnogalacturonan-binding receptor on activated T cells could be demonstrated Rhamnogalacturona n was reported to enhance cytotoxicity of CD56+ NK cells by effector c ell/target cell bridging. Untreated CD3+ cells hardly reacted with rha mnogalacturonan and IL-2-activated T cells showed only a moderate enha ncement of cytotoxicity in the presence of rhamnogalacturonan. However , when CD3+ T cells had interacted with anti-CD3 antibodies during cel l-sorting or during subsequent culturing with IL-2, enhancement in cyt otoxicity and increased formation of lytic effector cell/tumour cell c onjugates in the presence of rhamnogalacturonan could be readily demon strated, indicating a bridging effect analogous to CD56 + NK cells. Th e conjugate formation of activated T cells with tumour cells as well a s the additional rhamnogalacturonan-mediated bridging must be based on the expression of receptors with acetyl mannose specificity, since en hancements of MHC-unrestricted T cell cytotoxicity and conjugate forma tion were inhibited in a dose-dependent manner when acetylated mannose was present in the assays.