Microphage

Microphage is a historical term used to describe small phagocytic leukocytes, primarily neutrophils, and sometimes eosinophils, in contrast to macrophages, which are larger phagocytes derived from monocytes. The name comes from Greek roots meaning “small eater.”

Historically, microphages were distinguished from macrophages by size, lifespan, and tissue localization. Microphages were viewed as rapid, short-lived responders that arrive quickly to sites of infection, while macrophages were seen as longer-lasting cells involved in tissue remodeling and antigen presentation.

Function and cell types. The principal microphages are neutrophils, the most abundant circulating white blood cells, which rapidly migrate to inflamed or infected tissue and perform phagocytosis of bacteria and debris, release antimicrobial substances, and contribute to inflammation. Eosinophils can also participate in phagocytic activities, though they play a smaller or more specialized role in immune defense. In modern immunology, neutrophils and eosinophils are described by their specific lineages rather than under the umbrella term microphage. Neutrophils are known for their granule enzymes and respiratory burst during pathogen destruction.

Modern usage and relevance. The term microphage is largely historical and is rarely used in contemporary textbooks, which prefer terminology based on distinct cell types (neutrophil, eosinophil) and on macrophages for monocyte-derived large phagocytes. Nevertheless, the concept reflects an early attempt to categorize phagocytic cells by size and function within the innate immune system.

See also: macrophage, neutrophil, phagocytosis, innate immunity.