Generation of the alloreactive T-cell repertoire: interaction of T-cell genotype and maturation environment.

The influences of the T-cell genotype and the T-cell maturation environment on generation of the T-cell alloreactive repertoire were evaluated in cytotoxic T-lymphocyte responses to Kb mutant determinants expressed by the strains B6. C-H-2bm1 and B6-H2-bm6. By constructing bone marrow chimeras using either H-2b of H-2d mice as the source of donor cells and either H-2d or H-2b irradiated mice as recipients, it was first determined whether the T-cell major histocompatibility complex genotype alone determines the alloreactive repertoire. The results of such experiments indicated that H-2b T cells that have matured in a normal H-2b environment (C57BL/6N, C57BL/10Sn) or H-2d T cells that have matured in a chimeric H-2b environment (B10.D2 leads to C57BL/10Sn) are responsive to Kbm1 and Kbm6 determinants while H-2b T cells that have matured in an H-2d chimeric environment (C57BL/10Sn leads to B10.D2) have a diminished responsiveness to H-2bm1 and are completely unresponsive to H-2bm6. These findings showed that T-cell genotype alone does not determine the alloreactive repertoire to mutant Kbm1 and Kbm6 determinants and suggested that the T-cell maturation environment plays a critical role in this process. Further studies were carried out to determine whether the T-cell maturation environment alone determines this repertoire, such that maturation in an H-2b but not in an H-2d environment is both necessary and sufficient to generate reactivity to Kbm6. Experiments in which either H-2d responder populations neonatally made tolerant to H-2b or unlabeled target blocking of normal H-2d responders were used provided evidence that T cells specific for Kbm6 mutant determinants are present in the repertoire of H-2d T cells that have matured in an H-2d environment. These findings suggest that the alloreactive T-cell repertoire is not determined by the T-cell major histocompatibility complex genotype alone or by the T-cell maturation environment alone but rather than it is the product of unique interactions between the two.