signal-regulatory protein α (SIRP α ， Signal regulatory protein α) It is a regulatory glycosylated membrane protein from the SIRP family, mainly expressed in bone marrow cells, stem cells, or nerve cells. signal-regulatory protein α (SIRP α) It is the most important member of the SIRP family. On the one hand, SIRP α It can be activated by various mitogens and undergo phosphorylation, binding to SHP-1 and SHP-2 through its ITIM domain to transmit inhibitory signals. On the other hand, SIRP α It can also inhibit downstream pathway activation and transmit negative signals by interacting with CD47 ligands. SIRP α It plays an important role in the regulation of natural immunity, and LPS can induce SIRP in macrophages through transcriptional inhibition and protein degradation pathways α Downregulation of expression, SIRP α Inhibition of MAPK, IKKs, NF by blocking the action of SHP-2- κ Activation of B and IRF3, reducing inflammatory factors and IFN β Release. Studies have shown that SIRP in dendritic cells (Dc) α It can also negatively regulate the function of DC and T cells in both directions by binding to CD47 on the surface of T cells. On the one hand, it inhibits the expression of IL-12R in T cells and reduces the responsiveness of adult CD4+and CD8+T cells to IL-12. On the other hand, it inhibits the phenotypic and functional maturation of immature DC and the release of cytokines.