Studies on the induction and expression of T cell-mediated immunity. IX. Activation of alloimmune memory lymphocytes into specific secondary CTL by syngeneic NAGO-oxidized stimulator cells

Secondary cytotoxic thymus-derived lymphocytes (CTL) with specificity for the priming alloantigen are shown to be generated by in vitro stimulation of allosensitized memory splenocytes with NAGO-oxidized syngeneic, allogeneic, or xenogeneic cells. The cell surface aldehyde resulting from NAGO modification of stimulator cells is required for triggering both lymphocyte proliferation and secondary (2°) CTL activation, since treatment with the reducing agent, KBH₄, completely inhibited these responses. Compared to alloantigen stimulation, NAGO-oxidized stimulator cells induced an earlier peak of proliferation (2 to 3 vs 4 to 5 days), whereas the peak of the cytotoxic activity was identical (days 3 to 4). Syngeneic splenocytes, peripheral T cells, plastic and nylon nonadherent cells, and the P388D₁ macrophage-like cell line were all efficient stimulators after NAGO modification. Stimulation by syngeneic cells was shown to be mitomycin C resistant, U.V. irradiation sensitive, and ineffective when heat killed cells are used. Therefore, NAGO stimulation is distinct from antigen specific activation whereby U.V. treated cells, heated cells and nonviable membrane fragments have been shown to differentiate memory cells into 2° CTL. In addition, neither NAGO-treated sheep red blood cells nor syngeneic thymocytes were found to be effective stimulators. The addition of specific anti-Ia serum to the culture fluid inhibited both the proliferative and cytotoxic response, suggesting a role for an Ia signal during NAGO stimulation. These results show that the signal(s) required for the activation of 2° CTL from memory populations can be provided by certain subpopulations of NAGO-modified cells and is also dependent on the presence of Ia or an Ia-like molecule.