Cell-cell interactions for CD23 expression and soluble CD23 release from peripheral lymphocytes of atopic donors.

The cell-cell interactions for CD23 expression and soluble (s)CD23 release from peripheral blood lymphocytes (PBL), as well as purified cells (B, T cells, monocytes) of atopic donors, were studied. Cells either stimulated combined and subsequently separated or stimulated after separation were analysed. IL-4, IL-2, phytohaemagglutinin (PHA), interferon-gamma (IFN-gamma) and the combined interaction of IL-4 and IFN-gamma as well as PHA and IFN-gamma were used as stimuli. sCD23 release in the cell supernatant was determined from cells separated before stimulation. CD23 expression induced by IL-4 on cells stimulated and subsequently separated was significantly lower compared with amounts on separated cells which were subsequently stimulated. Major expression of CD23 was obtained on B cells and monocytes. Stimulation with PHA led to an increased expression on T cells compared to the control. When cells were stimulated, combined and separated, the combined stimuli of IL-4 and IFN-gamma showed a reduced CD23 expression for both experimental procedures and an enhanced release of sCD23. The data suggest an important role for cell-cell interactions. These results were supported by experiments in which separated cells were either co-cultured or cultured in Transwells. Co-culture of T cells with B cells and monocytes suggested that T cells are responsible for suppressed CD23 expression. No or only slight enhancement was obtained for sCD23 release. Our data indicate that cell-cell interactions and cytokines regulate CD23 expression, while sCD23 release is apparently solely regulated by soluble mediators (e.g. cytokines).