Receptors and ligands implicated in human T cell costimulatory processes.
It is well established that full activation of T cells that recognize antigens requires additional signals. These second signals are generated by the interaction of costimulatory ligands expressed on antigen presenting cells with their receptors on T cells. In addition, T cell activation processes are negatively regulated by inhibitory costimulatory pathways. Interaction of members of the B7 and the TNF superfamilies with members of the CD28 and TNF-R-superfamilies plays major roles in costimulatory processes. However, a large number of molecules that do not belong to these families have been reported to be involved in the generation of T cell costimulatory signals. In addition to well-defined costimulatory pathways, where both receptors and ligands are known, there are many T cell surface molecules that have been described to generate a second signal under certain experimental conditions, f.i. when ligated with antibodies. Furthermore there are several ligands that have been shown to positively or negatively modulate T cell activation by interacting with as of yet unknown T cell receptors. Here we give a comprehensive overview of molecules that have been implicated in human T cell activation processes and propose criteria that define genuine T cell costimulatory pathways.
Leitner
Judith
J
Institute of Immunology, Center for Physiology, Pathophysiology and Immunology, Medical University of Vienna, Borschkegasse 8a, 1090 Vienna, Austria.
Grabmeier-Pfistershammer
Katharina
K
Steinberger
Peter
P
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism; D006801:Humans; D008024:Ligands; D008213:Lymphocyte Activation / Q000276:immunology*; D051379:Mice; D011948:Receptors, Antigen, T-Cell / Q000276:immunology* / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*
D008024:Ligands; D011948:Receptors, Antigen, T-Cell