Functional Characterization of Human B Cells Carrying the Lymphocyte Large Sialoglycoprotein gpl50

Human B cell-enriched populations were prepared from buffy coats of healthy donors. By means of affinity chromatography, the B cells were separated into two fractions, one enriched in and the other depleted of cells expressing gp150, the large sialoglycoprotein of lymphocytes. In the presence of autologous T cells, monocytes and pokeweed mitogen B cell populations enriched for gp150+ cells gave rise to significantly more plasma cells (cIg+ cells) and secreted significantly more IgG than gp150-depleted populations. In contrast, more or an equal amount of IgM was secreted in cultures containing gp150-depleted cells. The differences between the fractions could not be ascribed to uneven distribution of T3+ cells, OKM1+ cells or B1+ (CD20) cells. However, the gp150-enriched population contained significantly more B2+ (CD21) cells than the gp150-depleted population. These results suggest that the gp150+ B cells differ from gp150- B cells, not only in their responsiveness to T cell differentiation signals but also in their commitment to Ig heavy chain isotype secretion.