The expanding B7 superfamily: increasing complexity in costimulatory signals regulating T cell function |
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Authors: | Coyle A J Gutierrez-Ramos J C |
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Institution: | Millennium Pharmaceuticals Inc, Inflammation Division, Cambridge, MA 02139, USA. Coyle@mpi.com |
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Abstract: | Upon encounter with specific antigen, na?veT helper precursor (THP) cells become activated. This event is regulated not only by engagement of the T cell receptor (TCR) with peptide presented in the context of major histocompatibility complex (MHC) class II molecules but by a number of costimulatory signals. CD28 engagement by B7-1 and B7-2 on resting THP cells provides a critical signal for initial cell cycle progression, interleukin 2 production and clonal expansion. However, largely as a consequence of the unraveling of the human genome, it is becoming clear that B7-1 and B7-2 are part of a larger family T of related counter-receptors that play an essential role in regulating the fate of primed, rather then resting,THP cells. These molecules play an important sequential role and act, together with B7-1- and B7-2-primed T cells, in the acquisition of effector function and/or tolerance induction. |
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