Functional uncoupling of T-cell receptor engagement and Lck activation in anergic human thymic CD4+ T cells.
Human thymic CD1a-CD4+ T cells in the final stage of thymic maturation are susceptible to anergy induced by a superantigen, toxic shock syndrome toxin-1 (TSST-1). Thymic CD4+ T-cell blasts, established by stimulating human thymic CD1a-CD4+ T cells with TSST-1 in vitro, produce a low level of interleukin-2 after restimulation with TSST-1, whereas TSST-1-induced adult peripheral blood (APB) CD4+ T-cell blasts produce high levels of interleukin-2. The extent of tyrosine phosphorylation of the T-cell receptor zeta chain induced after restimulation with TSST-1 was 2-4-fold higher in APB CD4+ T-cell blasts than in thymic CD4+ T-cell blasts. The tyrosine kinase activity of Lck was low in both thymic and APB CD4+ T-cell blasts before restimulation with TSST-1. After restimulation, the Lck kinase activity increased in APB CD4+ T-cell blasts but not in thymic CD4+ T-cell blasts. Surprisingly, Lck was highly tyrosine-phosphorylated in both thymic and APB CD4+ T-cell blasts before restimulation with TSST-1. After restimulation, it was markedly dephosphorylated in APB CD4+ T-cell blasts but not in thymic CD4+ T-cell blasts. Lck from APB CD4+ T-cell blasts bound the peptide containing the phosphotyrosine at the negative regulatory site of Lck-505 indicating that the site of dephosphorylation in TSST-1-activated T-cell blasts is Tyr-505. Confocal microscopy demonstrated that colocalization of Lck and CD45 was induced after restimulation with TSST-1 in APB CD4+ T-cell blasts but not in thymic CD4+ T-cell blasts. Further, remarkable accumulation of Lck in the membrane raft was observed in restimulated APB CD4+ T-cell blasts but not in thymic CD4+ T-cell blasts. These data indicate that interaction between Lck and CD45 is suppressed physically in thymic CD4+ T-cell blasts and plays a critical role in sustaining an anergic state.
Fujimaki
W
W
Department of Microbiology and Immunology, The Heart Institute of Japan, Tokyo Women's Medical University, Tokyo 162-8666, Japan. wakae@research.twmu.ac.jp
Iwashima
M
M
Yagi
J
J
Zhang
H
H
Yagi
H
H
Seo
K
K
Imai
Y
Y
Imanishi
K
K
Uchiyama
T
T
D000328:Adult; D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology; D001427:Bacterial Toxins; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D002478:Cells, Cultured; D017635:Clonal Anergy / Q000187:drug effects / Q000276:immunology*; D004768:Enterotoxins / Q000494:pharmacology; D006801:Humans; D007376:Interleukin-2 / Q000096:biosynthesis; D007739:L Cells; D008213:Lymphocyte Activation; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000378:metabolism*; D051379:Mice; D018448:Models, Immunological; D011948:Receptors, Antigen, T-Cell / Q000502:physiology*; D012397:Rosette Formation; D012756:Sheep; D018089:Superantigens / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D013950:Thymus Gland / Q000276:immunology
D001427:Bacterial Toxins; D004768:Enterotoxins; D007376:Interleukin-2; D011948:Receptors, Antigen, T-Cell; D018089:Superantigens; C030107:enterotoxin F, Staphylococcal; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck)