title: In vitro and in vivo evidence for high frequency of I-Ab-reactive CD4+ T cells in HLA-DQ or HLA-DRA transgenic mice lacking endogenous MHC class I and/or class II expression.
abstract: Although T cells are educated to recognize foreign antigenic peptides in the context of self MHC molecules during their development in the thymus, peripheral T cells also recognize allo- and xeno-MHC molecules. The lower frequency of xeno-MHC-reactive T cells than that of allo-MHC-reactive T cells is often explained by the difference in the degree of homology between xeno- or allo-MHC and self MHC molecules, as well as by the species barrier of the molecules involved in immune recognition. To distinguish these two possibilities, we estimated the frequency of I-Ab-reactive CD4+ T cells selected by HLA-DQ or DR alpha E beta b molecules, using HLA-DQ6 and HLA-DRA transgenic C57BL/6 (B6) mice lacking endogenous MHC class I and/or class II molecules (DQ6A0/0 and DR alpha 30A0/0 beta 20/0). CD4+ lymph node T cells from DQ6A0/0 and DR alpha 30A0/0 beta 20/0 showed the strong proliferative response to I-Ab molecules. In addition, DQ6A0/0 and DR alpha 30A0/0 beta 20/0 rejected the skin graft from mice expressing I-Ab molecules irrespective of MHC class I expression, indicating that the CD4+ T cells recognizing I-Ab molecules are directly involved in this rejection. The estimated frequency of I-Ab-reactive CD4(+)CD8- thymocytes in DR alpha 30A0/0 beta 20/0 and DQ6A0/0 was comparable with that observed in the MHC class II-disparate strains. Our findings thus indicate that CD4+ T cells selected to mature on xeno-MHC class II molecules such as HLA-DQ6 or DR alpha E beta b, when these molecules are expressed in mice, recognize I-Ab molecules as allo-MHC class II, despite the less structural homology.
authors.affiliation: Department of Genetics, Medical Institute of Bioregulation, Kyushu University, Fukuoka.
authors.forename: T
authors.initials: T
authors.lastname: Ishimoto
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Fukui
authors.forename: Y
authors.initials: Y
authors.lastname: Fukuda
authors.forename: K
authors.initials: K
authors.lastname: Dohi
authors.forename: T
authors.initials: T
authors.lastname: Sasazuki
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002478:Cells, Cultured; D005260:Female; D006084:Graft Rejection; D006683:HLA-DQ Antigens / Q000096:biosynthesis* / Q000235:genetics*; D006684:HLA-DR Antigens / Q000096:biosynthesis* / Q000235:genetics*; D059805:HLA-DR alpha-Chains; D000949:Histocompatibility Antigens Class II / Q000096:biosynthesis* / Q000235:genetics / Q000276:immunology*; D006801:Humans; D016130:Immunophenotyping; D018655:Lymphocyte Count; D007959:Lymphocyte Culture Test, Mixed; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D016038:Skin Transplantation / Q000276:immunology; D016176:T-Lymphocyte Subsets
chemical_list: D006683:HLA-DQ Antigens; C063831:HLA-DQ6 antigen; D006684:HLA-DR Antigens; D059805:HLA-DR alpha-Chains; D000949:Histocompatibility Antigens Class II