Mannose receptor mediated phagocytosis of bacteria in macrophages of blunt snout bream (Megalobrama amblycephala) in a Ca2+-dependent manner

• The tissue and cellular location of mannose receptor of blunt snout bream (Megalobrama amblycephala).
• Mannose receptor was involved in the phagocytosis of bacteria in macrophages of blunt snout bream.
• The MR-mediated phagocytosis was Ca2+-dependent.

Mannose receptor (MR) is an important pattern-recognition receptor in macrophages and plays a critical role in immune responses. It is has been reported that mammalian macrophages are able to engulf a wide range of microorganisms mediated by Ca2+-dependent MR binding to terminal mannose residues which are frequently found on the pathogen surfaces. However, little is known about the MR-mediated phagocytosis in macrophages of fish. In this report, the distributions of MR in the macrophage and head kidney tissue from blunt snout bream were examined using MaMR specific antibody generated in our lab. Mannan and MaMR specific antibody inhibition experiments results collectively showed that MR was involved in the GFP-expressed E. coli engulfed in the macrophages, resulting in respiratory burst, nitric oxide production as well as inflammatory cytokines secretion, and the MaMR-mediated phagocytosis was Ca2+-dependent. These results will shed a new light on the immune functions of teleost MRs.