Binding of mouse red blood cells (MRBC) by human thymocytes: augmentation of rosette formation by phospholipase C treatment.

The formation of rosettes with MRBC is not an exclusive property of chronic lymphocytic leukemia cells and of human B-lymphocytes. Human thymus cells and the HD-MAR T-cell line were also found to be capable of forming rosettes with MRBC. The binding of MRBC by thymocytes differed from that of sheep (SRBC), rabbit (RRBC) and human (HRBC) erythrocytes by a number of parameters: monoclonal antibodies against the E-receptor inhibited the attachment of SRBC, RRBC, and HRBC, but not of MRBC to thymus cells. The presence of EDTA had the opposite effect, abrogating only the attachment of MRBC to thymus cells but not of RBC from the other sources. Exposure of thymus cells to pronase eliminated their capacity to bind SRBC, RRBC, and HRBC, but only slightly inhibited the attachment of MRBC. Treatment with Vibrio cholerae neuraminidase enhanced the formation of rosettes with SRBC, RRBC, and HRBC, but had no effect on the formation of rosettes with MRBC. Exposure of thymus cells and of the HD-MAR cells to phospholipase C enhanced the proportion of rosettes formed with MRBC, but had no effect on the binding of other RBC. Treatment with either phospholipase A2 or phospholipase D had no such effect. The binding of MRBC by Raji cells was not increased by phospholipase C treatment. The present study indicates that the binding of MRBC by human thymus cells is mediated by receptors distinct from those involved in the binding of SRBC, RRBC, and HRBC and also from those mediating the binding of MRBC to human B-cells.