title: Characterization of H4: a mouse T lymphocyte activation molecule functionally associated with the CD3/T cell receptor.
abstract: The monoclonal antibody C398.4A was produced by immunizing Armenian hamsters with the mouse T cell clone D10.G4.1. It recognizes a molecule selectively expressed by activated mouse T cells and was named H4. H4 is expressed on the T cell surface about 24 h after activation and peaks at day 7. By contrast, it is not expressed by resting or activated B cells, macrophages, or fibroblasts. It is also expressed by CD4 or CD8 single-positive mature thymocytes. Immunoprecipitation showed that H4 is a disulfide-linked dimer, precipitating as a broad band at about 50-65 kDa under nonreducing conditions and at 25 and 29 kDa under reducing conditions. Deglycosylation of the reduced H4 by N-glycanase gave rise to a single band of about 21 kDa, suggesting that the two chains may be differentially glycosylated forms of the same protein. The H4 expression pattern and biochemical features, together with cross-blocking, co-capping, co-modulation, and immunoprecipitation preclearing experiments showed that H4 is different from other known co-stimulatory molecules such as CD69, CD2, Ly-6, CD25, OX-40, Mac-1 and LFA-1. By in vitro kinase assay, H4 was found to co-precipitate a tyrosine kinase activity that phosphorylated substrates of about 29 and 25 kDa. Co-modulation and co-capping experiments showed that H4 is physically associated with the CD3/T cell receptor. These data suggest that H4 may function as a T cell-specific co-stimulatory molecule and play a role in the T cell response when the activation stimulus is limited either because the antigen is only available in low concentration or has a low agonistic activity.
authors.affiliation: Divisione Universitaria di Ematologia, Dipartimento di Medicina e Oncologia Sperimentale, Università di Torino, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Redoglia
authors.forename: U
authors.initials: U
authors.lastname: Dianzani
authors.forename: J M
authors.initials: JM
authors.lastname: Rojo
authors.forename: P
authors.initials: P
authors.lastname: Portolés
authors.forename: M
authors.initials: M
authors.lastname: Bragardo
authors.forename: H
authors.initials: H
authors.lastname: Wolff
authors.forename: D
authors.initials: D
authors.lastname: Buonfiglio
authors.forename: S
authors.initials: S
authors.lastname: Bonissoni
authors.forename: C A
authors.initials: CA
authors.lastname: Janeway
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000945:Antigens, Differentiation, T-Lymphocyte / Q000502:physiology*; D006224:Cricetinae; D003412:Cricetulus; D016130:Immunophenotyping; D008213:Lymphocyte Activation; D051379:Mice; D011233:Precipitin Tests; D011505:Protein-Tyrosine Kinases / Q000276:immunology; D017260:Receptor-CD3 Complex, Antigen, T-Cell / Q000502:physiology*; D015398:Signal Transduction / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology / Q000378:metabolism*
chemical_list: D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte; D017260:Receptor-CD3 Complex, Antigen, T-Cell; D011505:Protein-Tyrosine Kinases