title: Lack of evidence for aggregation-dependent enhancement of p56lck in the signal transduction upon major histocompatibility complex recognition by mature T cells.
abstract: The kinase activity of lymphocyte-specific tyrosine kinase p56lck (Lck) upon physiological major histocompatibility complex (MHC) recognition by normal mature T cells was examined. Recognition of the target MHC molecules by T cells induced phosphorylation of the zeta-chain without obvious enhancement of the background Lck activity. There was no sign of enhancement of Lck through putative T-cell receptor (TCR)-independent class II MHC/CD4 interactions either. As has been reported, cross-linking of CD4 molecules by antibodies induced a marked enhancement of Lck activity. However, it did not have an immediate relevance to TCR-mediated signal transduction, as judged from the lack of detectable de novo phosphorylation of zeta-chain and the absence of functional responses of T cells. These results strongly favour the model in which TCR-mediated signal transduction does not involve aggregation-dependent enhancement of Lck, suggesting that the signal can be triggered simply by the recruitment of already active Lck with basal kinase activity through the formation of a TCR/MHC/CD4 ternary complex.
authors.affiliation: Department of Immunology, Kitasato University School of Medicine, Sagamihara, Japan. eshima@med.kitasato-u.ac.jp
authors.forename: Koji
authors.initials: K
authors.lastname: Eshima
authors.forename: Harumi
authors.initials: H
authors.lastname: Suzuki
authors.forename: Nobukata
authors.initials: N
authors.lastname: Shinohara
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000378:metabolism; D002449:Cell Aggregation / Q000276:immunology; D002478:Cells, Cultured; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism*; D008285:Major Histocompatibility Complex / Q000276:immunology*; D051379:Mice; D008822:Mice, Transgenic; D010766:Phosphorylation; D011948:Receptors, Antigen, T-Cell / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology*; D013601:T-Lymphocytes / Q000201:enzymology / Q000276:immunology*
chemical_list: D011948:Receptors, Antigen, T-Cell; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)