Up-regulation of receptors for IgA on activated human B lymphocytes.

Abstract

Expression of receptors for the Fc part of IgA (Fc alpha R) by T lymphocytes was recently shown to be up-regulated after activation by T cell mitogens in the absence of IgA. We describe a similar increase on activated human B lymphocytes. Fc alpha R were determined by labelling with human secretory IgA (0.5 mg/ml) and flow cytometry analysis after staining with fluoresceinated goat anti-IgA or goat anti-secretory component F(ab')2 fragments. B-enriched cell suspensions were prepared from peripheral blood or tonsils and activated by Staphylococcus aureus Cowan I, anti-IgM antibodies or E. coli lipopolysaccharide. All three activators increased the percentage of Fc alpha R positive cells although only the former induced significant DNA synthesis. Finally recombinant interleukin 1 (10 nM) and interleukin 2 (10 IU/ml) but not interleukin 4 (300 units/ml) nor low-molecular-weight B cell growth factor induced an increase of Fc alpha R expression. The data show that Fc alpha R can be up-regulated on human B cells in the absence of exposure to IgA.