FIG. 7.

Absence of MHC class I L^d-specific, HvG-directed cytolytic activity in the lungs of mixed chimeras. Pulmonary infiltrate lymphocytes isolated at the peak of lung infiltration were tested for ex vivo cytolytic activity at the indicated effector-to-target (E/T) cell ratios on target cells expressing L^d (A; parental P815 mastocytoma), L^d plus B7-1 (B; transfectant P815-B7), and L^d plus Fas (C; transfectant P815-Fas). Insets show the cytofluorometric analyses verifying the expression of B7-1 and Fas by the respective transfectants, as well as their absence on parental P815. FL, log FITC fluorescence intensity. The total CTL activity contained in the tested lymphocyte population was determined by the TCR redirected lysis assay using a MAb directed against TCR α/β bound to Fc receptors that are expressed constitutively by P815 (D). All target cells expressed surface L^d as detected by cytofluorometry, and all were lysed by a CTL line specific for L^d (not shown).