DIFFERENTIAL REGULATION OF LFA-1 AND ICAM-1 ON HUMAN PRIMARY B-LYMPHOCYTES

Changes in adhesive properties play important regulatory roles in activation and differentiation of B-cells. To better understand the regulation of interactions between B-cells and other cells during the immune response, we have studied surface expression of the adhesion molecules LFA-1 (CD11a/CD18) and ICAM-1 (CD54). Both adhesion molecules were upregulated during B-cell activation. However, upon stimulation with anti-IgM and IL-4, ICAM-1 levels started to increase within 12 hr, while LFA-1 levels did not start to increase until after 36 hr. When B-cells were stimulated with the PKC activator PDB and a calcium ionophore, ICAM-1 levels, but not LFA-1 levels, increased. Only if these activators were removed after around 24 hr of activation and the cells were recultured in fresh medium was there an eightfold induction of LFA-1. Such reculturing in fresh medium led, however, to decreased ICAM-1 levels.