612 Antibody Receptor on B Lymphocytes

Ant ibody-ant igen complexes bind to the surface of some mouse lymphocytes (1-2). Recent evidence has suggested tha t this proper ty may be characteris t ic of some nonthymus-der ived "B" lymphocytes: (3), not of thymus-der ived " T " lymphocytes (4). A similar conclusion has been reached independent ly in our laboratory from studies originally designed to examine the relat ionship between antigen-binding cells and "memory" cells in pr imed mice. In these experiments, use was made of the sensitive technique of rad ioautography to establish the presence of a receptor for ant ibody on lyrnphocytes. Thoracic duct lymphocytes (TDL) were selected as the main source of lymphoid cells because of their high viabi l i ty and low contaminat ion with other cell types. The ident i ty of lymphocytes binding ant ibody was established by examination of cell populat ions either enriched for T cells or B cells or containing the two cell types in known numbers. The T cell content was assessed by means of independent genetic markers such as 0 C3H antigen or H-2 antigen in the case of chimeric mice. When this figure was compared with the proport ion of antibody-binding lymphocytes , an inverse relationship was observed. An exact correlation was therefore demonstrable between the number of lymphocytes binding ant ibody and the number of B cells in the population. In other words, the receptor is carried by all B cells, not by just a subclass of B cells. The identification of a marker of this kind on all B cells has permi t ted the develop-