Signal Regulatory Protein Alpha-Fc Gamma Receptor pathway (SIRPα-FcγR pathway)

The Signal Regulatory Protein Alpha-Fc Gamma Receptor (SIRPα-FcγR) pathway is a crucial immunological signaling mechanism that regulates phagocytic responses in immune cells, particularly in macrophages and other myeloid cells. It operates through the interplay of two key receptor systems: the inhibitory receptor SIRPα, which binds to CD47 to generate negative "don't eat me" signals via ITIMs and SHP-1/2 phosphatases, and activating Fc gamma receptors (FcγRs), which recognize IgG antibodies and trigger pro-phagocytic "eat me" signals via ITAMs and SYK kinases. This pathway plays a vital role in determining the threshold for phagocytosis and shaping broader immune responses by integrating and balancing these opposing activating and inhibitory signals.

Drugs targeting the SIRPα-FcγR pathway primarily aim to modulate the delicate balance between inhibitory SIRPα signaling and activating FcγR signaling. This often involves blocking the interaction between SIRPα and its ligand CD47 to disinhibit FcγR-mediated phagocytosis, particularly in cancer immunotherapy. Other therapeutic strategies might involve directly modulating FcγR activation or enhancing SIRPα inhibitory signals to control immune responses in various diseases.