IDENTIFICATION OF A NOVEL FUNCTIONAL 85-KD GLYCOPROTEIN RESTRICTED TOLONG-TERM DIVIDING HUMAN LYMPHOCYTIC LINES

Lymphocyte activation induces or increases the expression of several s urface structures, some of which are directly involved in cell growth such as receptors for IL2 or transferrin. To identify new structures c haracteristic of activated lymphocytes, we developed a series of mAbs against functionally defined human T-cell clones or the NK-mediating c ell line YT2C2. In this study, we report the isolation of an mAb terme d AY19 recognizing, at the cell surface, an 85-kD glycoprotein whose e xpression is restricted to T-lymphocyte clones, leukemic T-cell lines, and T-ALL peripheral blood cells. Biochemical studies, as well as phe notypic analysis, revealed that this structure is different from all p reviously identified molecules on the cell surface of lymphocytes. Fur thermore, functional studies showed that triggering of this 85-kD stru cture on cloned T-lymphocytes through the AY19 epitope led to an inhib ition of CD3-induced proliferation. These findings suggest that the AY 19 mAb defines a T-cell antigen expressed mainly on long-term dividing lymphocytes and, therefore, its putative ligand might play a role in the regulation of T-lymphocyte growth induced by CD3-TcR stimulation.