Mixed lymphocyte reaction (MLC) of T-lymphocytes with dendritic cells is one of the basic tools for studying of immune reaction mechanisms. This work describes a new method of evaluation of allogeneic and autologous MLC by flow cytometry and differential gating. This method is based on fixed time acquisition of events and their sorting according to their forward and side scatter properties. Differential gating distinguishes populations of all living cells (R1), living nonproliferating cells (R2) and dead/apoptotic cells (R4). Addition of fluorescence microspheres (R3) enables the calculation of absolute number of cells in a given sample volume. Using the method of 7-AAD exclusion, we have shown that approximately 90% of 7-AAD positive cells project into the R4 gate. Moreover, there was an excellent correlation between the R1: R2 ratio and the percentage of cells positive for activation/proliferation marker CD71. The method of differential gating in its basic version does not require use of any fluorescent antibody and therefore is suitable for rapid screening of large number of samples at reasonable cost and without the use of radiolabeled nucleotides.

        Key words: flow cytometry – mixed lymphocyte reaction – T-lymphocytes – dendritic cells.