Rosette formation between rat thymocytes and guinea pig erythrocytes requires “active” fetal calf serum: II. Characterization of the receptor-bearing thymocytes

Abstract High proportions of thymocytes from many rat strains participate in rosette formation (RF) with guinea pig erythrocytes only in the presence of non-heated fetal calf serum. Adult Lewis rat spleens, lymph nodes, peripheral blood and bone marrow contain very few cells capable of participating in RF. Adult levels of cells participating in RF are present in Lewis rat thymus from the perinatal period onward. Essentially, no cells participating in RF are found in the spleens or bone marrow of Lewis rats during the perinatal period. Thymocytes participating in RF are sensitive to high doses of cortisone and low doses of irradiation in vivo . After sublethal irradiation, thymuses are rapidly repopulated by cells participating in RF. After lethal irradiation followed by bone marrow transplantation, thymuses are repopulated by donor cells that can participate in RF. Of interest, a moderate proportion of thymocytes from many mouse strains also can participate in RF. This subpopulation of murine thymocytes are highly cortisone sensitive.