What term describes molecules that facilitate receptor-ligand interaction by binding to the receptor and helping its coordination?

• A. Antigens
• B. Coreceptors
• C. Ligands
• D. Enzymes

Answer: (B)

Coreceptors are molecules that facilitate receptor-ligand interactions by binding to the receptor and helping coordinate the binding with the ligand. They don’t usually bind the ligand directly; instead, they stabilize the receptor-ligand complex and often recruit signaling molecules to boost the response. A classic example is on T cells, where CD4 or CD8 binds to MHC on an antigen-presenting cell and brings the TCR into a configuration that enhances signaling, via recruitment of kinases like Lck. This makes the receptor-ligand interaction more effective and initiates downstream signaling.

Antigens are the molecules that the immune system recognizes; ligands are the primary binding partners for receptors; enzymes catalyze chemical reactions. The term that fits this description is coreceptors.