Table 1.
Natural history and main functions of macrophages, mast cells and neutrophils
| Characteristic | Macrophages | Mast cells | Neutrophils |
|---|---|---|---|
| Difference in phenotype | F4/80+ (mouse) or EMR1+ (human), CD107b+ (Mac-3+), CD68+ | c-Kithi, FcεRIhi (including the αβγγ form of FcεRI; some macrophages and neutrophils can express the αγγ form of FcεRI); prominent cytoplasmic granules, some of which contain tryptase and/or contain heparin | Ly6G+, MPO+, polylobed nucleus |
| Origin of precursor cells | Bone marrow | Bone marrow | Bone marrow |
| Site of maturation | Almost all tissues (a few in the bone marrow) | Almost all tissues (a few in the bone marrow) | Bone marrow |
| Mature cells in the circulation | No (or very few) | No (except in mast cell disorders such a mastocytosis) | Yes |
| Mature cells recruited into tissues from circulation | No (immature monocytes migrate into tissues) | No (mast cell progenitors migrate into tissues) | Yes (during innate or acquired immune responses) |
| Mature cells normally reside in connective tissues | Yes | Yes | No (not detectable by microscopy) |
| Proliferative ability of mature cells | May vary by subpopulation (M2 macrophages can proliferate under certain circumstances) | Yes (under certain circumstances) | None reported |
| Lifespan | Weeks to months | Weeks to months (on the basis of studies of rodents) | Days (like other granulocytes) |
| Phenotypically distinct subpopulations in different tissues | Yes (Fig. 1) | Yes (Fig. 2) | Not reported |
| Phagocytosis | Yes | Reported, but biological importance not fully understood | Yes |
| Detect pathogens and danger signals and help to initiate inflammation | Yes (including near surfaces exposed to the environment) | Yes (including near surfaces exposed to the environment) | Yes (for example, in the blood or at sites of ongoing inflammation) |
| Enhance inflammation | Yes | Yes | Yes |
| Limit or suppress inflammation | Yes | Yes | Yes |
| Promote tissue repair | Yes | Yes | Yes |
| Antigen presentation | Yes | Reported, but biological importance is uncertain | Reported, but biological importance is uncertain |
| Degrade or detoxify components of animal venoms | Not reported | Yes | Not reported |