title: Self-class I MHC molecules support survival of naive CD8 T cells, but depress their functional sensitivity through regulation of CD8 expression levels.
abstract: Previous studies have suggested that naive CD8 T cells require self-peptide-major histocompatability complex (MHC) complexes for maintenance. However, interpretation of such studies is complicated because of the involvement of lymphopenic animals, as lymphopenia drastically alters naive T cell homeostasis and function. In this study, we explored naive CD8 T cell survival and function in nonlymphopenic conditions by using bone marrow chimeric donors and hosts in which class I MHC expression is absent or limited to radiosensitive versus radioresistant cells. We found that long-term survival of naive CD8 T cells (but not CD4 T cells) was impaired in the absence of class I MHC. However, distinct from this effect, class I MHC deprivation also enhanced naive CD8 T cell responsiveness to low-affinity (but not high-affinity) peptide-MHC ligands. We found that this improved sensitivity was a consequence of up-regulated CD8 levels, which was mediated through a transcriptional mechanism. Hence, our data suggest that, in a nonlymphopenic setting, self-class I MHC molecules support CD8 T cell survival, but that these interactions also attenuate naive T cell sensitivity by dynamic tuning of CD8 levels.
authors.affiliation: Center for Immunology, Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN 55455, USA.
authors.forename: Kensuke
authors.initials: K
authors.lastname: Takada
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Jameson
mesh_terms: D000818:Animals; D016827:CD8 Antigens / Q000235:genetics*; D018414:CD8-Positive T-Lymphocytes / Q000502:physiology*; D002470:Cell Survival; D005786:Gene Expression Regulation; D015395:Histocompatibility Antigens Class I / Q000502:physiology*; D016130:Immunophenotyping; D053699:Interleukin-7 Receptor alpha Subunit / Q000032:analysis; D008213:Lymphocyte Activation; D051379:Mice; D008810:Mice, Inbred C57BL; D020395:Receptors, Interleukin-7 / Q000502:physiology; D018183:Transplantation Chimera
chemical_list: D016827:CD8 Antigens; D015395:Histocompatibility Antigens Class I; D053699:Interleukin-7 Receptor alpha Subunit; D020395:Receptors, Interleukin-7; C415350:interleukin-7 receptor, alpha chain