title: Apparent split tolerance of CD8+ T cells from beta 2-microglobulin-deficient (beta 2m-/-) mice to syngeneic beta 2m+/+ cells.
abstract: beta 2-microglobulin-deficient (beta 2m-/-) mice express reduced levels of MHC class I molecules and, consequently, have impaired positive selection of CD8+ T lymphocytes in the thymus. However, small numbers of CD8+ CTLs can be found in beta 2m-/- mice after immunization with allogeneic as well as syngeneic beta 2m+/+ tumor or spleen cells. It has been proposed, therefore, that because of the low ligand density in beta 2m-/- mice, negative selection does not remove cells capable of recognizing syngeneic MHC class I expressed at normal levels. We report here that beta 2m-/- CD8+ T cells are partially tolerant to syngeneic beta 2m+/+ cells. Despite the ability of beta 2m-/- mice to raise CD8+ CTLs against syngeneic beta 2m+/+ cells, these CD8+ cells do not proliferate and do not secrete IFN-gamma or IL-3/granulocyte-macrophage-CSF upon in vitro stimulation with syngeneic beta 2m+/+ cells. In contrast, all of these cellular responses are displayed by the beta 2m-/- CD8+ cells upon recognition of the allogeneic MHC class I. These in vitro findings of partial responsiveness to syngeneic and of full responsiveness to allogeneic MHC class I correlate well with the ability of beta 2m-/- mice to reject allogeneic, but not syngeneic, tumors in vivo. It appears, thus, that the significantly reduced levels of MHC class I molecules found in beta 2m-/- mice, although not capable of inducing deletion of all reactive clones, can induce deletion of high affinity clones and, therefore, maintain tolerance to self-MHC class I, even when expressed at much higher (beta 2m+/+) levels.
authors.affiliation: Department of Pathology, New York University Medical Center, New York 10016, USA.
authors.forename: K G
authors.initials: KG
authors.lastname: Jhaver
authors.forename: T D
authors.initials: TD
authors.lastname: Rao
authors.forename: A B
authors.initials: AB
authors.lastname: Frey
authors.forename: S
authors.initials: S
authors.lastname: Vukmanović
mesh_terms: D000818:Animals; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D003429:Cross Reactions; D003602:Cytotoxicity, Immunologic; D015395:Histocompatibility Antigens Class I; D007108:Immune Tolerance; D007114:Immunization; D066298:In Vitro Techniques; D007519:Isoantigens; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D001613:beta 2-Microglobulin / Q000172:deficiency / Q000235:genetics / Q000276:immunology*
chemical_list: D015395:Histocompatibility Antigens Class I; D007519:Isoantigens; D008222:Lymphokines; D001613:beta 2-Microglobulin