CD28 binding to B7-1 on antigen-presenting cells (APCs) prov...

created [InstanceEdit:388731] Garapati, P V, 2008-12-16 10:42:53
dbId 388726
displayName CD28 binding to B7-1 on antigen-presenting cells (APCs) prov...
literatureReference
modified [InstanceEdit:9927288] Tiwari, Krishna, 2024-11-05
schemaClass Summation
text CD28 binding to B7-1 on antigen-presenting cells (APCs) provides a crucial costimulatory signal that enhances T cell activation. This interaction modulates antigen recognition by T cells and ensures full activation in conjunction with T-cell receptor (TCR) engagement. Despite the homodimeric nature of CD28, it interacts with B7-1 in a manner that mimics a single binding site. The V-like domain of CD28 features the conserved MYPPPY motif within the CDR3-analogous loop, which is critical for the recognition and binding of its ligands. Both B7-1 and B7-2 interact with CD28 at overlapping, though non-identical, binding sites, contributing to nuanced modulation of T cell activation (Linsley et al. 1994, Truneh et al. 1996).
CTLA4 primarily affects CD28 costimulation by acting as a competitive inhibitor. CTLA-4 has a much higher affinity for these ligands compared to CD28. When CTLA-4 binds to B7-1 or B7-2, it prevents these ligands from interacting with CD28, thereby reducing the costimulatory signals that are crucial for T cell activation (van der Merwe et al. 1997).
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