Use of immunotolerance to dissect the mechanisms regulating appearance of hapten-specific killer T cells <i>in vivo</i>.

Abstract

Abstract In efforts to delineate the mechanism that regulates the in vivo appearance of hapten-specific killer T cells stimulated by hapten-conjugated syngeneic lymphoid cells, we utilized two different immunotolerance techniques directed to the hapten. We have found that the method by which tolerance is induced toward the hapten determines whether hapten-specific killer T cells will be generated in vivo. When nascent hapten was injected to induce tolerance before initiating sensitization for CML and DTH, both parameters were found to be depressed. However, adoptive transfer of spleen cells from such tolerant animals hindered development of only DTH in the new hosts. Furthermore, incorporation of spleen cells from such tolerant animals into the effector phase of hapten-specific cytotoxic lymphocytes generated in vivo or in vitro did not prevent killer T cells from performing their function. When hapten-coupled syngeneic spleen cells were injected i.v. to induce tolerance, DTH but not CML was found to be controlled. Thus, this method for inducing tolerance apparently is unable to regulate CML. Furthermore, spleen cells from animals made tolerant by hapten-coupled cells, when incorporated into the effector phase of CML that had been initiated in vitro, did not deter the attack of T killer cells on hapten-modified targets. Soluble suppressor factor, a product of T suppressor cells that arises after tolerance induction, was examined for its capability to alter the afferent and efferent limbs of hapten-specific CML. It was shown to suppress neither, in spite of the fact that it affects both arms of the hapten-specific DTH response. These findings are compatible with the view that stimulation of helper cells in vivo, by providing an auxiliary cell possessing allogeneic antigens, circumvents the suppressor cell system that normally operates to prevent a T killer response to altered self as well as the suppressor cell system that arises as a consequence of tolerance induction. Furthermore, neither the killer T cells nor the haptenated syngeneic cell appear to be targets of the suppressor cells and/or its product(s) that depress DTH.