The conformational flexibility of class I H-2 molecules as revealed by anti-peptide antibodies specific for intracytoplasmic determinants: differential reactivity of beta 2-microglobulin "bound" and "free" H-2Kb heavy chains.
Immunoprecipitation experiments using anti-peptide antisera prepared against exon 6, exon 7 and exon 8-encoded intracytoplasmic regions of the H-2Kb gene product indicated that approximately 1/3 of the H-2Kb heavy chains in a cell surface-labelled glycoprotein fraction from EL-4 cells, or H-2b spleen cells, is not associated with beta 2-microglobulin (beta 2-m). This population of "free" H-2Kb heavy chains failed to react with alloantisera or monoclonal antibodies specific for conventional H-2Kb serological determinants, suggesting that significant conformational alterations were induced in the extracellular domains upon dissociation of beta 2-m. In addition, although antibodies to intracytoplasmic peptide 8 were able to react with both "free" and beta 2-m "bound" heavy chains, the determinants seen by anti-peptide 6 and anti-peptide 7 were only recognized in the "free" heavy chain. These data suggest that the conformational perturbation of the extracellular domains induced by beta 2-m dissociation can be "transmitted" to the intracytoplasmic region of the heavy chain. These results indicate the potential for a class I heavy chain-mediated transmembrane signalling event, and suggest that the "free" class I heavy chain might have a role to play in the major histocompatibility complex (MHC)-restricted presentation of T-cell determinants to cytotoxic T-lymphocytes.
Department of Immunology, University of Toronto, Canada.
M H
MH
Smith
B H
BH
Barber
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D003593:Cytoplasm / Q000276:immunology*; D015180:Electrophoresis, Gel, Two-Dimensional; D000939:Epitopes / Q000276:immunology*; D006183:H-2 Antigens / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D010455:Peptides / Q000276:immunology; D011233:Precipitin Tests; D011487:Protein Conformation; D001613:beta 2-Microglobulin / Q000276:immunology* / Q000378:metabolism
D000911:Antibodies, Monoclonal; D000939:Epitopes; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; D010455:Peptides; D001613:beta 2-Microglobulin