Modulation of B-cell colony growth by T-cell subsets

The ability of T-cell subsets to modulate the growth of B-cell colonies derived from human peripheral blood mononuclear cells (PB-MNC) was analyzed. B-cell-enriched populations (BCE), isolated by depletion of E-rosetting cells, were placed in the upper agar layer of a double-layer agar system. The lower layer contained the mitogen Staph Protein A (5-10 micrograms/ml). Colonies of B cells (100-500/4 X 10(5) cells) were observed in cultures containing BCE, partially depleted of T cells by a single cycle of E-rosetting. Rigorous depletion of T-lymphocytes from BCE by an anti-T-cell antibody and C' decreased colony numbers to approximately 25% of control values. Addition of autologous T cells to underlayers restored B-cell colony growth in a dose-dependent fashion. OKT4 cells were more effective than OKT8 cells in enhancing colony responses. OKT8 cells, however, did not suppress B-cell colony growth. The ability of T cells to enhance proliferation of B cells was unaffected by irradiation. These data indicate that T cells amplify proliferation of human B-cell colonies and that different subsets of T cells vary in their ability to support B-cell colony growth.