[The in vitro proliferative response of human peripheral blood lymphocytes stimulated with purified concanavalin A and the analysis of subpopulations of T-cells (author's transl)].

Human peripheral blood lymphocytes (PBL) were separated from anticoagulated peripheral blood using the Ficoll-Conraxin-L gradient technique, and were cultured with various concentrations of highly purified concanavalin A (Con A (F3)). Tritiated thymidine incorporation in these cultures was measured. PBL responded well to low doses of Con A (F3) and high doses of Con A (F3), and the dose-response curve to Con A (F3) of PBL seemed to show that bimodal proliferative response with a notch or a peak at 5--6 micrograms/ml of Con A (F3) and the other peak at the higher doses of Con A (F3). As it has been well known that E-rosette-forming cells (E-RFC) in human peripheral blood can be subdivided into two T-cell subpopulations on the basis of their relative affinity for sheep red blood cell (SRBC), we have examined how these T-cell subpopulations could responded to Con A (F3) at varying concentrations. We found that "Low-affinity E-RFC" could be optimally stimulated by Con A (F3) at 5--6 micrograms/ml, while "High-affinity E-RFC" at 8--12 micrograms/ml. 3H-thymidine incorporation of high-affinity E-RFC was strikingly increased at low doses of Con A (F3) when low-affinity E-RFC and high-affinity E-RFC were mixed at 25: 75 ratio, and the dose-response curve was very similar to that of PBL. Moreover when monocytes were added to high affinity E-RFC and the mixture was cultured, the doses-response curve was elevated at low doses of Con A (F3), but the dose-response curve was similar to that of high-affinity E-RFC and different from that of low-affinity E-RFC. Our results suggest that low-affinity E-RFC that has the capacity to respond optimally to Con A (F3) at 5--6 micrograms/ml in the in vitro proliferative response has the important effect upon the in vitro proliferative response of PBL to low doses of Con A (F3).