Imaging antigen recognition by naive CD4+ T cells: compulsory cytoskeletal alterations for the triggering of an intracellular calcium response.
Antigen recognition was analyzed at the single-cell level by using for the first time T cells which were not altered by in vitro selection, transfection or immortalization. The first consequence of antigen recognition by ex vivo naive CD4+ T cells from T cell receptor (TCR)-transgenic mice is the formation of a "contact zone" with the B cell presenting the antigen. The T cell intracellular calcium (Ca2+) response begins after a delay of 30 s on average, following the formation of the contact zone. The T cell response is entirely inhibited by either protein tyrosine kinase or actin polymerization inhibitors but, surprisingly, it is insensitive to inhibitors of phosphoinositide 3-kinase. Moreover, inhibition of microtubule polymerization and use of Ca2+-free medium do not prevent the beginning of the T cell response, but do reduce the stability of the contact zone and/or the amplitude of the Ca2+ plateau. The critical involvement of the cytoskeleton in antigen recognition on B cells introduces a checkpoint in T cell activation: the initial TCR engagement triggers a Ca2+ response only after an amplification step corresponding to a cytoskeleton-controlled increase in the number of engaged TCR.
Delon
J
J
Laboratoire d'Immunologie Cellulaire, URA CNRS 625, Paris, France.
Bercovici
N
N
Liblau
R
R
Trautmann
A
A
D000199:Actins / Q000502:physiology; D000818:Animals; D017951:Antigen Presentation; D000941:Antigens / Q000378:metabolism* / Q000502:physiology; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D002450:Cell Communication / Q000276:immunology; D048429:Cell Size / Q000276:immunology; D003599:Cytoskeleton / Q000276:immunology / Q000378:metabolism*; D000939:Epitopes / Q000378:metabolism; D007399:Interphase / Q000276:immunology; D007424:Intracellular Fluid / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D016693:Receptors, Antigen, T-Cell, alpha-beta / Q000235:genetics; D015398:Signal Transduction / Q000276:immunology; D014404:Tubulin / Q000502:physiology
D000199:Actins; D000941:Antigens; D000939:Epitopes; D016693:Receptors, Antigen, T-Cell, alpha-beta; D014404:Tubulin