Peripheral (somatic) expansion of the murine cytotoxic T lymphocyte repertoire. II. Comparison of diversity in recognition repertoire of alloreactive T cells in spleen and thymus of young or aged DBA/2J mice transplanted with bone marrow cells from young or aged donors.

Lethally irradiated (1000 R whole body) DBA/2J mice of 10 wk or 20 mo of age were repopulated with anti-Thy-1.2-treated DBA/2J bone marrow cells of 10-wk- or 20-mo-old donors. Sixty days post-transplant, limiting dilution cultures of the spleen and thymus cell population of individual mice (for each group) were examined to assess the within-group and between-group diversity in the anti-H-2Kb allo-recognition repertoire. Our data are consistent with a significant expansion of the CTLp repertoire taking place in the periphery, beyond the early appearing specificities present in the thymus. Moreover, comparison of the repertoires in young recipients of young or aged marrow, or in aged recipients of young or aged marrow, support the notion that there is a defect in the peripheral environment of aged mice that results in altered expansion of the thymic CTLp repertoire. In addition, there is an intrinsic difference in bone marrow precursor cells of CTLp in aged mice that is revealed only in an aged environment.