Nedocromil sodium acts directly on human B cells to inhibit immunoglobulin production without affecting cell growth.

The effect of nedocromil sodium (NES) on human immunoglobulin (Ig) isotypes, IgG subclasses and IgA subclasses was studied. NES inhibited IgM and IgA1 production from human lymphoblastoid B-cell lines CBL and GM-1056, respectively, in a dose-dependent fashion. This inhibition was not due to decreased cell growth as cell proliferation was not affected by NES and cell viability was always greater than 98%. Of the various cytokines tested, interleukin-4 (IL-4) reduced the NES-induced inhibition of Ig production, whereas other cytokines, including IL-1 beta, IL-2, IL-3, IL-5, IL-6, interferon-alpha (IFN-alpha), IFN-gamma, granulocyte-macrophage colony-stimulating factor (GM-CSF) and erythropoietin (Epo) failed to do so. The reducing effect of IL-4 was blocked by anti-IL-4 antibody but not by control IgG. Moreover, IFN-alpha and IFN-gamma, but not GM-CSF, overcame the reducing effect of IL-4. NES also inhibited production of IgM, IgG1, IgG2, IgG3, IgG4, IgA1 and IgA2 by tonsillar B cells stimulated with Staphylococcus aureus Cowan strain I (SAC) and IL-6 without affecting proliferation. This inhibition was reduced by IL-4 specifically. These results indicate that in addition to its anti-allergic function, NES may act as a B-cell regulatory reagent.