In vitro effect of immunosuppressives on the percentage of CD14+CD16+ monocytes peripheral blood monocytes collected from a healthy donor were cultured in the presence of rATG, basiliximab and methylprednisolone. Changes of CD16 expression on the surface CD14-positive monocytes were measured at following time points: 0, 1, 3, 6, 24, 48 and 72 h. Incubation with rATG (a) downregulated the proportion of CD14+CD16+ monocytes already after one hour. Basiliximab (b) had no effect. Methylprednisolone (c) upregulated the percentage of CD14+CD16+ subpopulation. Dynamics of the parameters was fitted by quadratic regression and the estimated coefficients were compared by z-statistcs.