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Thymic medullary type epithelial cell line (MTEC1), which expressed H|2D d and Ia+d, was derived from BALB/c mouse. MTEC1 cells were introduced by intrathymic injection into irradiated H|2+b mice reconstituted with H|2 b×d F1 bone marrow cells. Two months later, the injected MTEC1 cells were found to be still present in the recipient thymus. Splenocytes from chimeric mice, in %in vitro% functional assays, were analyzed to investigate whether the MTEC1 cells %in vivo% could induce the production of H|2+d restricted antigen|specific T cells. The H|2+d restricted VSV|antigen specific proliferating and IL|2 producing T cells as well as H|2+d restricted influenza virus specific cytotoxic T cells were found in chimeric mice injected with MTEC1 cells, and these cells were shown to be tolerant to H|2+d self|antigen. On the contrary, H|2+d restricted antigen|specific and H|2+d self|antigen tolerant T cells were not shown in control mice injected with saline. These results suggest that intrathymically injected MTEC1 cells could induce T lineage cell development and functional maturation in the intact thymus. A hypothesis of “second thymic selection” in thymic medulla has been postulated and its implication discussed.
Thymic medullary type epithelial cell line (MTEC1), which expressed H | 2D d and Ia + d, was derived from BALB / c mouse. MTEC1 cells were introduced by intrathymic injection into irradiated H | 2 + b mice reconstituted with H | 2 b × d F1 bone marrow cells. Two months later, the injected MTEC1 cells were found to be still present in the recipient thymus. Splenocytes from chimeric mice, in % in vitro % functional assays, were analyzed to investigate whether the MTEC1 cells % in vivo could have induced the production of H | 2 + d restricted antigen | specific T cells. The H | 2 + d restricted VSV | antigen specific proliferating and IL | 2 producing T cells as well as H | 2 + d restricted influenza virus specific cytotoxic T cells were found in chimeric mice injected with MTECl cells, and these On the contrary, H | 2 + d restricted antigen | specific and H | 2 + d self | antigen tolerant T cells were not shown in control mi ce injection with saline. These results suggest that intrathymically injected MTEC1 cells could induce T lineage cell development and functional maturation in the intact thymus. A hypothesis of “second thymic selection ” in thymic medulla has been postulated and its implied discussed.