title: Expression and function of mixed isotype MHC class II molecules in normal mice.
abstract: Mixed isotype MHC class II molecules (E alpha dA beta d) occur at extremely low levels on the surface of normal mouse B cells and macrophages, as determined by surface staining with an E alpha dA beta d-specific hamster mAb, H71-258.41. The surface levels of mixed isotype on the B cell lymphoma line A20 are approximately 1 to 2% that of surface I-A, whereas the levels of these molecules on normal mouse B cells were estimated to be at least two to four times less than those on A20. Nevertheless, other investigators have recently reported that immunization of normal H-2d mice with the sperm whale myoglobin peptide 110-121 (SWM(110-121)) elicits T cells, predominantly, V beta 8.2+, that recognize the peptide only in context of E alpha A beta. We have characterized a large number of SWM(110-121)-specific T cell hybridomas from several strains of H-2d haplotype mice. All of the V beta 8.2+ 110-121-specific hybridomas were found to be restricted by E alpha dA beta d, whereas, of the V beta 8.2- 110-121-specific group, approximately half recognized the peptide through E alpha dA beta d whereas the remainder were restricted by either I-Ad or I-Ed. mAb inhibition experiments revealed that 14-4-4S (E alpha-specific) could block presentation by mixed isotype completely, while MK-D6 (A beta d-specific) and H71-258.41 (E alpha dA beta d-specific) only inhibited presentation when the concentration of peptide was limiting. Although A20 expresses very low levels of mixed isotype, 10 to 100 nmol of the peptide produced a detectable response, illustrating the remarkable efficiency in presenting this peptide through E alpha dA beta d. The ability of normal mouse APC to use this restriction element despite its extremely low expression has important implications for the activation of T cells by low levels of peptide-MHC complexes.
authors.affiliation: Department of Medicine, National Jewish Center for Immunology and Respiratory Medicine, Denver, CO 80206.
authors.forename: J S
authors.initials: JS
authors.lastname: Spencer
authors.forename: J H
authors.initials: JH
authors.lastname: Freed
authors.forename: R T
authors.initials: RT
authors.lastname: Kubo
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D017951:Antigen Presentation; D001402:B-Lymphocytes / Q000276:immunology; D002460:Cell Line; D006224:Cricetinae; D000949:Histocompatibility Antigens Class II / Q000737:chemistry / Q000378:metabolism*; D006825:Hybridomas / Q000276:immunology; D008264:Macrophages / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D008811:Mice, Inbred DBA; D008814:Mice, Inbred NZB; D011487:Protein Conformation; D013601:T-Lymphocytes / Q000276:immunology
chemical_list: D000911:Antibodies, Monoclonal; D000949:Histocompatibility Antigens Class II