T-cell influence on the B-cell differentiation process induced by Klebsiella

Klebsiella pneumoniae K43 cell membrane preparations (Klebs M) have been characterized previously as a human polyclonal B cell activator (PBA) that stimulates purified B cells to differentiate into immunoglobulin (Ig) secreting cells with negligible prior or parallel proliferation and in the absence of T cells. The aim of the present study was to define the cellular interactions in the regulation of Klebs M induced B-cell differentiation. For this purpose OKT4⁺ and OKT8⁺ cell populations were negatively selected with reasonable purity by means of a panning technique or by complement-mediated cytolysis using monoclonal OKT4 and OKT8 antibodies. The resulting cell populations were added to purified autologous B cells exposed to Klebs M or, as a control, pokeweed mitogen (PWM). In the Klebs M system both the OKT4⁺ and the OKT8⁺ cell subsets markedly enhanced IgM production; however, the helper effect of the OKT4⁺ cell subset was much more intense than that of the OKT8⁺ subset. In the PWM system only the OKT4⁺ cells provided help for B-cell differentiation. The OKT8⁺ subset demonstrated suppressor activity in the presence of an adequate helper cell (OKT4⁺ subset) function. These results indicate that Klebs M behaves like a "relatively T cell-independent PBA".