The T11 glycoprotein is functionally linked to a calcium channel in precursor and mature T-lineage cells

Human T lymphocytes are activated through either the antigen/major histocompatibility complex receptor (T3-Ti) or the T11 sheep erythrocyte-binding protein. Spectrofluorimetry and multiparameter flow cytometric techniques were utilized to examine the relationship of activation to alterations in cytoplasmic free calcium concentration, [Ca2+]i. T3-Ti receptor-triggered elevation in [Ca2+]i was found to be dependent in large part (approximately equal to 80%) on extracellular Ca2+ and to a much smaller extent (approximately equal to 20%) on mobilization of internal Ca2+ pools. Furthermore, T11-mediated increases in [Ca2+]i were entirely dependent on extracellular Ca2+. Though the kinetics of [Ca2+]i changes induced by monoclonal antibodies to T3-Ti and T11 differed, both pathways were otherwise similar, particularly with regard to effects on or mediated by the plasma membrane potential. Importantly, the T11 pathway was found to be functional in precursor T-lineage cells lacking the surface T3-Ti complex. These findings suggest that there may be a plasma membrane Ca2+ channel functionally or physically linked to the T11 structure or, alternatively, that there is a set of related T11- and T3-Ti-associated Ca2+ channels.