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Normal human red blood cells have an average life span of about 120 days in the circulation after which they are engulfed by macrophages. This is an extremely efficient process as macrophages phagocytose about 5 million erythrocytes every second without any significant release of hemoglobin in the circulation. Despite large number of investigations, the precise molecular mechanism by which macrophages recognize senescent red blood cells for clearance remains elusive.

SOURCE:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8006275/#:~:text=Normal%20human%20red%20blood%20cells,they%20are%20engulfed%20by%20macrophages.