Characterization of an Lyt-1+ cytolytic T-cell clone specific for a polymorphic domain of the I-Ak molecule.

We have characterized a cytolytic T-cell clone, isolated from a A.TH anti-A.TL mixed lymphocyte culture, which recognized a private determinant of the I-Ak molecule. This specificity has been confirmed by inhibition of effector-target cell interaction by anti-I-Ak monoclonal antibody (mAb). Comparison of the inhibitory capacity of various mAb and the spatial arrangement of their epitopes (defined in previous studies by antibody-binding competition) indicated that the antigenic site recognized by this cytolytic T-cell clone was topologically related to one of the major polymorphic domains of the Ak molecule. This clone expressed the Thy-1.2+, Lyt-1.+, Lyt-1.2+low and I-As- cell surface phenotype. Testing of several rat mAb, screened for their ability to inhibit H-2K/D-specific cytolysis at the level of the effector cells, revealed that two anti-p94, 180 mAb but not various anti-Lyt-2 mAb inhibited the lytic function of this anti-I-Ak T-cell clone.