Two B-cell subpopulations identified by flow cytometry.

Ig+ spleen cells were analysed by light scatter analysis on a flow cytometer and two distinct subpopulations were identified. The large Ig+ cells (10-11 micron in diameter) were found in spleen and bone marrow, whereas the small Ig+ cells (7-8 micron in diameter) were found in all lymphoid tissues. Of the total Ig+ splenic lymphocytes, 40-60% were large Ig+ cells and had surface IgM, Ia and Fc gamma receptors. The large Ig+ cells were highly enriched for responsiveness to the B-cell mitogens, anti-Ig, Nocardia water-soluble mitogen and LPS, whereas the small Ig+ splenic cells had little or no responsiveness to these mitogens.