Influence of cytokines and cellular interactions on the glucocorticoid-induced Ig (E, G, A, M) synthesis of peripheral blood mononuclear cells.

We studied the mechanisms of action leading to the glucocorticoid (GC)-induced synthesis of the immunoglobulins (IgE, G, A, M) by human peripheral blood mononuclear cells (PBMC). It is shown that the enhanced Ig synthesis of GC-stimulated PBMC is dependent on the presence of T cells and monocytes. After stimulation of purified B cells with GC only a slight enhancement of IgM could be detected. Inhibition studies with neutralizing anti-interleukin-4 (IL-4) and anti-IL-6 antibodies revealed that the GC-induced IgE synthesis of PBMC is not dependent on the presence of IL-4 or IL-6. Stimulation of membrane-separated and co-cultured cell fractions revealed that the GC-induced enhancement of IgA and IgM synthesis is mediated by T-cell derived soluble mediators. The GC-induced IgG and IgE synthesis is dependent upon contact of B cells with monocytes. Antibodies against LFA-1 and ICAM-1 are capable to suppress the GC-induced IgE and IgG synthesis of PBMC. Furthermore, the monocyte expression of lymphocyte function antigen-1 (LFA-1), intercellular adhesion molecule-1 (ICAM-1) and HLA-DR is modulated by GC stimulation.