The effect of cytokines, including IL-1, IL-4, and IL-6, in hairy cell proliferation/differentiation.

IL-1, IL-4, and IL-6 had no effect on hairy cell (HC) proliferation in vitro. Anti-mu and low molecular weight B cell growth factor (LBCGF) and tumor necrosis factor alpha (TNF-alpha) stimulated the proliferation of a minor subpopulation of HCs detected by double immunocytochemical staining. None of these cytokines had any effect on HC differentiation as measured by immunoglobulin secretion. It is concluded that none of the above growth factors are central to HC proliferation in-vivo. Since alpha-interferon IFN-alpha, but not IFN-gamma, consistently inhibited any proliferation observed, it seems likely that this monokine has a direct antiproliferative effect in vivo.