Quantitative determination of anti-A-dependent cytotoxicity of human peripheral blood monocytes

A simple test is suggested for the quantitative measurement of the cytotoxic activity of human peripheral monocytes. Adherent cells are separated from non-adherent cells in the wells of the microtiter plates, thus tedious resuspension of effector cells can be omitted. Effector cell number is accurately determined by isotope labelling. Maximum of cytotoxic activity is measured in the enzyme-like kinetic model of cytotoxicity as a function of target cell number. It was found that 34.2-51.2% of unseparated peripheral blood mononuclear cells (PBMC) were adherent. More than 80% of these were shown to be monocytes by monoclonal antibodies and alpha-naphthyl acetate esterase (ANAE) staining. Depletion of SRBC rosette forming cells prior to adherence (PBMC, E-) resulted in enrichment of adherent cells (61.3-82.8%), which were exclusively monocytes. Cytotoxic activity of both adherent populations (PBMC and PBMC, E-) for human red blood cells sensitized with anti-A was determined experimentally and also extrapolated by using the Michaelis-Menten equation. It was estimated that one monocyte was able to lyse more than 4 erythrocytes.