Neuroscience

Macrophage

Biology

Gene

Germination

Innate immune system

Paleontology

Acquired immune system

In vitro

Immunology

Macrophage polarization

Inflammation

Context (archaeology)

Botany

Cell biology

Epigenetics

Genetics

Priming (agriculture)

Immune system

Annual Review of Pathology Mechanisms of Disease

Macrophages are a diverse set of cells present in all body compartments. This diversity is imprinted by their ontogenetic origin (embryonal versus adult bone marrow-derived cells); the organ context; by their activation or deactivation by various signals in the contexts of microbial invasion, tissue damage, and metabolic derangement; and by polarization of adaptive T cell responses. Classic adaptive responses of macrophages include tolerance, priming, and a wide spectrum of activation states, including M1, M2, or M2-like. Moreover, macrophages can retain long-term imprinting of microbial encounters (trained innate immunity). Single-cell analysis of mononuclear phagocytes in health and disease has added a new dimension to our understanding of the diversity of macrophage differentiation and activation. Epigenetic landscapes, transcription factors, and microRNA networks underlie the adaptability of macrophages to different environmental cues. Macrophage plasticity, an essential component of chronic inflammation, and its involvement in diverse human diseases, most notably cancer, is discussed here as a paradigm.

Diversity, Mechanisms, and Significance of Macrophage Plasticity