Polyclonal B-cell-activating factors produced by spleen cells of mice stimulated with a cell homogenate of Trypanosoma gambiense.
The effect of injection of a cell homogenate of Trypanosoma gambiense into mice on the production of soluble factors responsible for the induction of polyclonal B-cell activation (PBA) by their spleen cells was examined. PBA was induced by injection of the cell homogenate and was also detected in mice treated with either the serum or the spleen cells of mice treated with the cell homogenate. PBA-inducing activity became detectable in the serum and spleen cells as early as 12 h after injection of the cell homogenate, reached a peak on day 2, and then decreased. This activity was also detected in the culture medium of spleen cells obtained 2 days after injection of the cell homogenate. For determination of the type of spleen cells producing the PBA-inducing factor, the day 2 spleen cells were fractionated on the basis of differences in their adhesive properties. Spleen cells in the effluents from a Sephadex G-10 column (T and B cells) and a nylon wool column (T cells) and those adhering to a plastic flask (macrophages) all produced the PBA-inducing factor. The production of PBA-inducing factor by whole spleen cells and by cells adherent to the plastic flask was not affected by treatment with anti-Thy-1.2 antibody and complement. These data suggest that soluble factors derived from macrophages and T cells could contribute to the induction of PBA. The PBA-inducing activity in the conditioned medium was completely inactivated by treatment at pH 2.0, heating at 56 degrees C for 30 min, or exposure to 0.1% sodium dodecyl sulfate. The results are discussed in relation to cytokines that could affect B-cell activation.