Properties of bispecific rosette-forming cells. II. --Rosette formation by "educated" T-lymphocytes.

Normal thymus cells transferred into thymectomized and lethally irradiated syngeneic mice responded to stimulation with sheep erythrocytes by rosette formation with these erythrocytes. This response reached a peak on the 7th day and was not associated with any production of circulating antibodies. Rosettes produced by "educated" T-cells were inhibited by anti-theta serum as well as by anti-mouse Fab serum. Simultaneous stimulation of transferred thymocytes with sheep and pigeon erythrocytes provoked the appearance of a minority of cells simultaneously binding both types of erythrocytes. Depletion of B cells contaminating normal thymocyte populatins after passage through anti-mouse Ig coated columns before their transfer in thymectomized and irradiated recipients did not prevent the appearance of simple and double RFC. Moreover, when normal thymocytes or T-cells "educated" by allogeneic stimulation were incubated at 4 degrees C with anti-SRBC and anti-PRBC mouse sera a subsequent incubation at 37 degress of resulted in the dissociation of most passive rosettes formed at 4 degrees. Conversely similar incubation at 37 degrees of rosettes formed by actively immunized cells resulted in capping of about 50% simple and double rosettes. This redistribution of membrane receptors is proposed as a routine test for distinguishing active from passive rosettes.