Functional Characterization in Vitro of Two Human T-cell Subpopuiations with Different Affinities to Sheep Erythrocytes

Abstract

On the basis of their different abilities to form rosettes with unsensitized sheep erythrocytes (SRBC), two subpopuiations of human T lymphocytes were separated by the rosette sedi-mentation technique. In a series of in vitro experiments the T cells carrying high-avidity receptors for SRBC (‘active’ T cells) were shown to respond significantly better when stimulated with purified protein derivative (PPD) and allogeneic cells than the subpopulation carrying low-avidity reecplors ‘non-active’ T cells). On the other hand, the latter responded better to phytohaemaggiutinin, concanavalin A and pokcweed mitogen; it was likewise demonstrated that these cells were better stimulators in a mixed lymphocyte reaction. The role of monocytcs in mitogen and PPD responses was investigated by adding such cells to Fe-treated suspensions. These were found io be crucial for an optimal response of both subpopuiations. Furthermore, ditfereni patterns of activation were observed for the active and non-active cells. Especially interesting was the observation that the Con A response of the active fraction was more mono-cyte-dependent than that of the non-active one.