Resolvin D4 (RvD4) is a specialized pro-resolving mediator derived from docosahexaenoic acid . [1] It has been detected in human milk, in the dorsal pouch of mice before and after infection with S. aureus, and in untreated tissues from humans, mice, and sardines.[2][3] RvD4, at 10 ng/mouse, reduces neutrophil infiltration in zymosan A-induced peritonitis and, at 200 ng/mouse, diminishes neutrophil infiltration in response to S. aureus infection. [3] With isolated cells, RvD4 promotes phagocytosis of bacteria, opsonized zymosan A, and apoptotic neutrophils by human macrophages.[3] It also promotes the clearance of apoptotic neutrophils by human fibroblasts.[3]

Reference：
[1]. Serhan, C.N., and Savill, J. Resolution of inflammation: The beginning programs the end. Nature Immunology 6(12), 1191-1197 (2005).
[2]. Arnardottir, H., Orr, S.K., Dalli, J., et al. Human milk proresolving mediators stimulate resolution of acute inflammation. Mucosal. Immunol. 9(3), 757-766 (2016).
[3]. Winkler, J.W., Orr, S.K., Dalli, J., et al. Resolvin D4 stereoassignment and its novel actions in host protection and bacterial clearance. Sci.Rep. 6, (2016).