The effect of steroids on differentiation and function of cultured, mononuclear cells.

When monocytes had differentiated to macrophages during 8 days of culture in vitro without being exposed to steroids, neither the engulfement nor the digestion step of phagocytosis was found to be influenced by cortisol or the other steroids tested. This indicates that cortisol has no direct effect on the phagocytic function of macrophages in doses below 10(-1) mg/ml. Continuous exposure to cortisol during the period of differentiation resulted in a dose dependent inhibition of the differentiation of monocytes to macrophages. Testosterone, deoxycorticosterone and tetrahydrocortisol in concentration of 10(-1) mg/ml, tested in the same way were found to be toxic to the cells. In lower concentrations, however, these steroids were found to have no effect on the cultured cells. The impaired differentiation of monocytes is suggested as an additional explanation of the reduced number of macrophages appearing at the site of inflammation during cortisol treatment.