Specificity of an anti-murine B cell serum

An antiserum (ABS) specific for murine B cells was prepared in rabbits by immunization with lymph node cells from nude mice as reported previously (1). To make the antiserum specific for antibody-forming cell precursors (AFCP) extensive absorption was required with mouse serum, erythrocytes and thymus cells. Even after ABS was no longer cytotoxic for thymus cells, further absorption with thymus cells was necessary to make it ineffective for plaque-forming cells (PFC). The correlation between cells bearing C3- or Fc-receptors and the cells bearing antigen(s) to which ABS reacts was studied. In the residual spleen cells treated with ABS and complement, there were some EAg and EAmCm rosette-forming cells. There were also some spleen cells reacting with ABS even after depletion of C3- and/or Fc-receptor-bearing cells. These results show that the antigen(s) to which ABS reacts could be a marker on B cells different from C3- or Fc-receptors. Spleen cells reacting with ABS were compared with cells bearing C3- or Fc-receptors various days after birth. The cells sensitive to ABS increased in spleens earlier after birth than those with C3- or Fc-receptors.