Lyt phenotypes of primary cytotoxic T cells generated across the A and E region of the H‐2 complex

Six different cell‐mediated lympholysis (CML) combinations were established, four of which generated effector cells against the I‐E, and two against the I‐A molecule. The cell surface phenotype of effector cells was then determined by depletion of cytotoxic T lymphocyte (CTL) activity with antisera and rabbit complement (C) treatment. Both types of effector cells were completely eliminated by treatment with anti‐Thy‐1.2 antiserum plus C. Anti‐Lyt‐1.2 and C depleted anti‐A and anti‐E killer activity but did not eliminate CTL generated across a whole H‐2 difference. One out of three different batches of anti‐Lyt‐2.2 antiserum did not deplete anti‐A killer activity, while it efficiently eliminated CTL generated across the E region or whole H‐2 difference. However, two batches of anti‐Lyt‐2.2 antiserum depleted also anti‐A CTL activity. A quantitative difference between anti‐A and anti‐E CTL in terms of Lyt‐2 expression was demonstrated by significant differences in recovery of killer activity, after treatment of these two types of CTL with a wide concentration range of the same anti‐Lyt‐2.2 antiserum and C. Thus it is concluded that anti‐A killer cells have the cell surface phenotype of Thy‐1⁺, Lyt‐1, Lyt‐2↑, whereas anti‐E CTL are Thy‐1⁺, Lyt‐1↑, Lyt‐2←. The data are discussed in the context of a possible association of Lyt phenotypes of T cells with the type of MHC antigens they recognize.