REGULATION OF INFLAMMATION-PRIMED ACTIVATION OF MACROPHAGES BY 2 SERUM FACTORS, VITAMIN D-3-BINDING PROTEIN AND ALBUMIN

A very small amount (0.0005 to 0.001%) of an ammonium sulfate [50% sat urated (NH4)(2)SO4]-precipitable protein fraction of alpha(2)-globulin efficiently supported inflammation-primed activation of macrophages. This fraction contains vitamin D-3-binding protein essential for macro phage activation. Comparative macrophage activation studies with fetal calf serum, alpha(2)-globulin fraction, 50% (NH4)(2)SO4 precipitate, and purified bovine vitamin D-3-binding protein revealed that fetal ca lf serum and alpha(2)-globulin fraction appear to contain an inhibitor for macrophage activation while ammonium sulfate precipitate contains no inhibitor. This inhibitor was found to be serum albumin. When bovi ne serum albumin (25 mu g/ml) was added to a medium supplemented with 0.0005 to 0.05% (NH4)(2)SO4 precipitate or 1 to 10 ng of vitamin D-3-b inding protein per ml, activation of macrophages was inhibited.