Human autologous rosette-forming cells. IV. Functional role in T-cell activation.

Human autorosette-forming cells (auto-RFC), which represent a T4/leu 3a+ cell subset, were investigated for their functional role in T-cell activation. Peripheral blood lymphocytes from healthy subjects either remained unfractionated or were separated into recovered or depleted auto-RFC populations. The phytohemagglutinin P stimulation of these three cell suspensions induced normal levels of proliferation, whereas the pokeweed mitogen activation was significantly decreased in the auto-RFC-depleted population compared to the auto-RFC-recovered subset or unfractionated cells. All three cell suspensions produced IL-2 in response to PHA stimulation. However the levels of lymphokine released were significantly lower in the recovered auto-RFC fraction than in the depleted auto-RFC. After activation, using anti-Tac antibodies, the synthesis of IL-2 receptors was evidenced in all the cell fractions regardless of the presence or absence of auto-RFC. In addition, both auto-RFC absorbed IL-2 activity from a reference supernatant. Taken together, these data suggest that auto-RFC can be expanded by T-cell mitogens, and that once activated, they express IL-2 receptors, but represent a minor source of IL-2 production.