A comparison of membrane markers on rat cytotoxic cells

The antigenic characteristics of cytotoxic T cells (CTL) and cells mediating antibody-dependent cellular cytotoxicity (ADCC) were defined using monoclonal antibodies W3/13, W3/25 and MRC OX8, and compared with the phenotype of natural killer (NK) cells previously defined by these antibodies. CTL, ADCC effector cells and NK cells were also tested for expression of Ia antigen using MRC OX6 monoclonal antibody. The fluorescence-activated cell sorter was used to separate effector populations into antigen-positive and antigen-negative subsets, and the cytotoxicity of the resultant lymphocyte fractions was then assessed using a 6 hr 51Cr release assay and a quantitative method of analysis based on consideration of target cell lysis as an enzyme substrate reaction. CTL, ADCC effector cells and NK cells were W3/25 negative and OX6 negative. CTL were positive for W3/13 and OX8 antibody with no cytotoxicity in the W3/13 negative and OX8 negative fractions. In contrast, ADCC effector cells showed heterogeneity of staining with W3/13 and OX8 antibodies, with 50% cytotoxic activity in the W3/13 negative fraction, and 20-30% cytotoxic activity in the OX8 negative fraction. In parallel experiments, NK cells and ADCC effector cells showed identical marker heterogeneity when tested with W3/13 and OX8 antibodies.