Effect of dichloromethylene diphosphonate (Cl2-MDP) on bone resorption induced by PHA-stimulated human mononuclear cells in organ culture.

Human mononuclear cells stimulated by PHA caused resorption of fetal rat bones in tissue culture. Non-adherent cells alone failed to produce substantial bone resorbing activity. The mixed culture of adherent and non-adherent cells (1:40) produced significant bone mineral resorption in vitro. The bone resorption induced by human mononuclear cells stimulated by PHA required the presence of living bone tissue in culture. The bone resorbing effect caused by PHA-stimulated cells was blocked by dichloromethylene diphosphonate at 10(-5) M concentration, but mononuclear cells preincubated in diphosphonate containing media were capable to resorb fetal rat bone in tissue culture.