BACKGROUND AND PURPOSE The use of human intestinal alkaline phosphatase (IAP) has already been validated as a novel treatment for endotoxin lipopolysaccharide (LPS)-induced inflammatory diseases, which is mediated through IAP’ s ability to detoxify LPS. However, there has been little investigation into the full extent of IAP’ s physiological function. This study investigates IAP’s non-LPS related functions and clinical applications. EXPERIMENTAL APPROACH In this study, we use freshly extracted human leukocytes to study effects of a recombinant human intestinal alkaline phosphatase (recIAP) on secretion of TNF-ɑ and IL-6 by the leukocytes in absence of LPS. Physiological substrates of alkaline phosphatase and their dephosphorylated products at neutral pH including ATP, ADP, AMP and adenosine were employed to investigate their effects on secretion of TNF-ɑ by the leukocyte. KEY RESULTS We found that recIAP inhibit TNF-α and IL-6 secretion by freshly extracted human leukocyte in the absence of LPS. recIAP dephosphorylates ATP and ADP etc at physiological pH. The dephosphorylated products by recIAP including AMP and adenosine inhibit TNF-α secretion of the freshly extracted human leukocyte. CONCLUSIONS AND IMPLICATIONS Human leukocyte migrates into inflamed tissues and secretes TNF-α and IL-6. Thus, leukocyte plays an important role in inflammatory diseases. recIAP inhibits TNF-α and IL-6 secreted by freshly extracted human leukocyte in the absence of LPS. The results in this study indicate that recIAP is a promising therapeutic candidate for diseases related to leukocyte TNF-α and IL-6 secretion.