[Molecular pathways of T lymphocyte activation].
TRIGGERING T CELL ACTIVATION: A quiescent T cell must encounter an antigen presenting cell to become activated. The T receptor for the antigen delivers a first specific signal which alone is insufficient to trigger total T cell activation. A second signal independent of antigen recognition is furnished by the antigen presenting cell, leading to total activation. PATHWAYS CAPABLE OF DELIVERING THE SECOND SIGNAL: CD28 and CTLA-4 are two molecules capable of playing a powerful role in regulating immune response. The fate of B cells depends on the CD40 molecule they carry on their surface as well as on T cells which express its ligand. Adherence molecules CD11a/CD18 induce tight adherence between T cells and antigen presenting cells by binding their CD50 ligand (ICAM-3); this bond activates the T cell, completing the first signal. The CD2 pathway and its ligands, a constitutional expression on two partner cells, is a strong adherence pathway which also transmits two powerful activation signals for T cells. SEVERAL FUNCTIONAL STATES: These different activation pathways illustrate the subtle interaction between surface molecules, capable of inducing different functional states depending on the environment.
Bernard
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INSERM U 343 et Laboratoire Central d'Immunologie, Hôpital de l'Archet, Nice.
Bernard
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D000941:Antigens / Q000276:immunology; D006801:Humans; D008024:Ligands; D008213:Lymphocyte Activation; D013601:T-Lymphocytes / Q000276:immunology*
D000941:Antigens; D008024:Ligands