title: Molecular associations of IA antigens after T-B cell interactions. I. Identification of new molecular associations.
abstract: In this report we report the identification of novel molecular associations involving the MHC class II (Ia) Ag expressed on the surface of Ag-presenting B lymphocytes. Biosynthetically radiolabeled murine B cells were incubated for 2 h in the presence or absence of T lymphocytes before treatment with the cleavable cross-linking reagent dimethyl-3,3'-dithiobispropionimidate. Anti-Ia immunoprecipitates of solubilized cell extracts revealed novel cross-linked products of Mr 90,000 to 95,000 which, upon cleavage of the cross-linker, could in part be resolved into native Ia and other structures of approximately Mr 67,000. The detection of the cross-linked products was significantly enhanced in B cells that had been co-cultured with T lymphocytes, but not with other cell types, and co-culture with various monoclonal T cell lines resulted in different levels of enhancement. Detection of the 90- to 95-kDa cross-linked products appeared to be independent of the foreign Ag for which the T cells were specific and could be enhanced when either cell type was replaced by a plasma membrane fraction, indicating that it resulted from direct cell-cell contact. These results suggest that some proportion of the Ia glycoproteins expressed on the surface of B cells become associated with other structures of Mr 67,000 upon Ag-non-specific interactions between T and B lymphocytes.
authors: Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor 48109-0620.
authors: R A
authors: RA
authors: Shivdasani
authors: D W
authors: DW
authors: Thomas
mesh_terms: D000818:Animals; D000938:Antigen-Presenting Cells / Q000032:analysis / Q000276:immunology / Q000502:physiology; D001402:B-Lymphocytes / Q000032:analysis* / Q000276:immunology / Q000502:physiology; D002450:Cell Communication; D002460:Cell Line; D003432:Cross-Linking Reagents; D000939:Epitopes / Q000032:analysis; D000949:Histocompatibility Antigens Class II / Q000276:immunology / Q000302:isolation & purification*; D051379:Mice; D008807:Mice, Inbred BALB C; D008970:Molecular Weight; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000032:analysis* / Q000276:immunology / Q000502:physiology
chemical_list: D003432:Cross-Linking Reagents; D000939:Epitopes; D000949:Histocompatibility Antigens Class II