Abstract
Recent studies have shown that bovine blood monocytes represent a heterogeneous population of circulating cells with distinct phenotypic and functional properties. However, little is known about the heterogeneity of macrophages derived from different monocyte subsets. The current study aimed at investigating the functional heterogeneity of macrophages derived from the three bovine monocyte subsets regarding their capacity to influence the vitality of bovine blood neutrophils. Blood neutrophils were stimulated with culture supernatants from LPS-stimulated macrophages generated from different monocyte subsets. Vitality of stimulated neutrophils was analyzed by flow cytometry using the mitochondrial membrane potential probe JC-1. Similar to LPS, supernatant of stimulated monocyte-derived macrophages enhanced the life-span of neutrophils by reducing the percentages of apoptotic cells. The comparison between macrophages derived from different monocyte subsets showed that culture supernatants of macrophages derived from classical and intermediate monocytes induced the strongest anti-apoptotic effect on neutrophils. This suggests a role for macrophages derived from classical and intermediate monocytes rather than non-classical monocytes in prolonging the lifespan of neutrophils and therefore their contribution to innate immune defense during the acute phase of infection or inflammation.

Key words: Bovine monocyte subsets; neutrophil; vitality; monocyte-derived macrophages; apoptosis