E-ROSETTE FORMATION AT 37DEGREESC - PROPERTY OF MITOGEN-STIMULATED HUMAN PERIPHERAL-BLOOD LYMPHOCYTES

Peripheral blood lymphocytes from healthy humans formed stable E [erythrocyte] rosettes with sheep E (SRBC) at 37.degree. C after culture with phytohemagglutinin or the divalent cation ionophore A23187. Cells manifesting this phenomenon exhibited blast morphology, appeared by 16 h of culture, increased dramatically in percentage and absolute number of 62 h, and persisted in large numbers for the duration of culture (182 h). Unstimulated lymphocytes formed rosettes at 4.degree. C but not at 37.degree. C. Increased stickiness due to surface-bound lectin mitogen was not the cause of rosette formation at 37.degree. C. Formation of E rosettes at 37.degree. C was previously considered a property of lymphocytes less differentiated than the circulating T [thymus-derived] cell (e.g., thymocytes, leukemic lymphoblasts). This property can apparently be reexpressed during blastogenesis in culture. This observation demonstrates technical problems associated with the use of SRBC to quantitate lymphocytes with complement receptors (B [bone marrow-derived] cells) by the EAC [E + antibody + complement] rosette assay in culture. False positives resulted from 37.degree. C E rosette formation, but this was overcome by replacing the SRBC with guinea pig erythrocytes in the EAC assay.