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Positive selecting cell type determines the phenotype of MHC class Ib-restricted CD8⁺ T cells

Cho, Hoonsik, Bediako, Yaw, Xu, Honglin, Choi, Hak-Jong, Wang, Chyung-Ru
Proceedings of the National Academy of Sciences of the United States of America 2011 v.108 no.32 pp. 13241-13246
CD8-positive T-lymphocytes, animal models, epithelial cells, hematopoietic stem cells, immune response, niches, phenotype, transgenic animals
Several studies have demonstrated an apparent link between positive selection on hematopoietic cells (HCs) and an "innate" T-cell phenotype. Whereas conventional CD8⁺ T cells are primarily selected on thymic epithelial cells (TECs) and certain innate T cells are exclusively selected on HCs, MHC class Ib-restricted CD8⁺ T cells appear to be selected on both TECs and HCs. However, whether TEC- and HC-selected T cells represent distinct lineages or whether the same T-cell precursors have the capacity to be selected on either cell type is unknown. Using an M3-restricted T-cell receptor transgenic mouse model, we demonstrate that not only are MHC class Ib-restricted CD8⁺ T cells capable of being selected on either cell type but that selecting cell type directly affects the phenotype of the resulting CD8⁺ T cells. M3-restricted CD8⁺ T cells selected on HCs acquire a more activated phenotype and possess more potent effector functions than those selected on TECs. Additionally, these two developmental pathways are active in the generation of the natural pool of M3-restricted CD8⁺ T cells. Our results suggest that these two distinct populations may allow MHC class Ib-restricted CD8⁺ T cells to occupy different immunological niches playing unique roles in immune responses to infection.