Inulin (INU),as a plant polysaccharide,has attracted much attention due to its wide application value and enhancement of immune,anti-inflammatory,anti-tumor and other biological functions.The aim of this study was to investigate the effect of INU on the immune activity of macrophage RAW 264.7.The effects of INU on the proliferative activity and phagocytotic activity of RAW 264.7 macrophages were detected by cell counting kit-8 (CCK8) and neutral red test.The Griess assay and enzyme-linked immunosorbent assay (ELISA) were used to detect the release of nitric oxide (NO) and cytokines interleukin-1β (IL-1β),interleukin-6 (IL-6),and tumor necrosis factor-α (TNF-α) in cells.Real time fluorescence quantitative PCR (qPCR) was used to detect the gene expression levels of cytokines (IL-1β,IL-6,TNF-α),and Western blotting (WB) was used to detect the effects of INU on the expression of key proteins related to cyclooxygenase 2 (COX2),inducible nitric oxide synthase (iNOS),and mitogen activated protein kinase (MAPK) pathways in RAW 264.7 macrophages.The results showed that INU significantly enhanced the proliferative activity and phagocytosis activity of RAW 264.7 cells and promoted the secretion of NO and the expression levels of IL-1β,IL-6 and TNF-α (P<0.01).In addition,INU significantly up-regulated the protein expression of phosphorylated extracellular regulatory protein kinase (p-ERK) and phosphorylated p38 mitogen-activated protein kinase (p-p38) in COX2,iNOS and MAPK pathways in a concentration-dependent manner (P<0.01).In summary,INU can regulate the immune activity of macrophages through the ERK/p38MAPK pathway,and has a good ability of immune regulation.