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Specific Isolation of B Lymphocytes by Means of Their Receptor for Antigen-Antibody-Complement (Ag-Ab-C) Complexes


 A population of lymphocytes (CRL) from many mammalian species including man has a receptor for Ag-Ab-C complexes. CRL interact with sheep red blood cells (E) coated with antibody (A) and complement (C) forming rosettes (Bianco, C. and Nussenzweig, V., J. Exp. Med., 132: 702, 1970). In the mouse, CRL are part of the population of B lymphocytes (Dukor, P., Bianco, C. and Nussenzweig, V., in preparation). The interaction between CRL and EAC appears to be mediated by a receptor for modified C3 on the lymphocyte membrane. Papain fragments of rabbit γG anti-mouse C3 competitively inhibit and revert the binding of EAC to CRL. Based on this finding, a method has been devised to purify CRL, which consists of: 1) incubation of EAC with lymphocytes for rosette formation; 2) separation of rosettes by sedimentation in a linear bovine serum albumin (BSA) gradient (The purified clusters contain less than 5% free leukocyte contamination); 3) treatment of the clusters with papain fragments of anti-C3 antibodies in order to dissociate EAC from CRL; 4) separation of CRL from EAC by ultracentrifugation in a discontinuous BSA gradient.