Background: LILRA3 is a soluble receptor with unknown functions that is abundantly present in human serum. Results: Optimally glycosylated recombinant LILRA3 protein produced only in a mammalian system binds potential ligands and suppresses monocyte function. Conclusion: LILRA3 suppresses LPS-mediated TNF production, suggesting that it is a new anti-inflammatory protein.Significance: This work provides first insight into the biochemical characteristics and functions of LILRA3.