Flow cytometric studies of IL-4-stimulated expression of the CD25 antigen by quiescent human B lymphocyte subpopulations.

The membrane immunoglobulin (mIg) phenotype of high-density human tonsillar B lymphocytes which display elevated levels of the CD25 marker in response to treatment with interleukin-4 (IL-4) has been investigated. IL-4 promotes elevation of CD25 levels in B lymphocytes expressing membrane IgM (mIgM), mIgD, mIgG and mIgA. Three-colour flow cytometric analyses indicate that 25-35% of high-density tonsillar B cells are simultaneously positive for mIgM, mIgD and CD25 following IL-4 stimulation. The hypothesis that B cells could respond to IL-4 by up-regulation of either CD23 or CD25, but not both simultaneously, was evaluated. Three-colour flow cytometric studies indicated that approximately one-third of the B-lymphocyte population was simultaneously positive for the CD19, CD23 and CD25 antigens following stimulation with IL-4. These data are consistent with the proposal that IL-4 can promote expression of CD23 and CD25 antigens in the same B lymphocyte.