Figure 1.

IL‐17A stimulates bone marrow (BM) stroma cells to secrete G‐CSF, and G‐CSF mediates granulopoiesis. Neutrophils in the BM are attached to stroma cell‐derived factor‐1α (SDF‐1α), which is present in BM stroma or on the surfaces of osteoblasts, reticular cells, and endothelial cells. The attachment is mediated by CXCR4 on neutrophil surfaces. G‐CSF downregulates CXCR4 expression on neutrophils and reduces SDF‐1α level in the BM, disrupting the attachment. Neutrophils released from SDF‐1α migrate into peripheral circulation to keep neutrophil homeostasis. Anti‐IL‐17A antibody interferes with IL‐17A‐mediated granulopoiesis and neutrophil migration from the BM and presumably interrupt neutrophil infiltration into AD brain