Production of osteoclast-activating factor by normal human peripheral blood rosetting and nonrosetting lymphocytes

This study has tested the ability of human mononuclear cells and the subpopulations of lymphocytes that rosette (E-RFC) or do not rosette (non-E-RFC) with sheep red blood cells to synthesize DNA and to produce a mediator with bone resorbing activity (osteoclast-activating factor, OAF) in response to stimulation with phytohemagglutinin (PHA). Mononuclear cells were stimulated by PHA both to synthesize DNA and to produce a factor that caused bone resorption. E-RFC enriched for T lymphocytes and depleted of macrophages synthesized considerable DNA in response to stimulation with PHA, but were unable to produce significant bone resorbing activity in tissue culture unless macrophages were re-added to the E-RFC. In contrast, mononuclear cells depleted of E-RFC (non-E-RFC enriched for B cells) did not synthesize DNA in response to stimulation with PHA, but did produce a mediator that caused significant bone resorption in tissue culture. In most of the experiments, unstimulated non-E-RFC produced as much OAF as the PHA-stimulated non-E-RFC. These results suggest that both activated T lymphocytes (E-RFC) and B lymphocytes (non-E-RFC) can produce OAF.