Death, eaters, and dark marks

Abstract

The maintenance of macrophage populations, role of environmental cues in shaping their physiology, and the response of resident cells to perturbation are critical factors in tissue homeostasis with implications for many pathological scenarios. Pigment-containing cells of the dermis are the latest to come under the scrutiny of a mouse-induced depletion model.

Insight from Matthew Collin

(A) In parallel with the mouse, human dermal macrophages show side scatter (SSC) low and high properties, depending on the level of melanin ingestion, as indicated by sorting, cytospin, and Giemsa stain (top). Tattoo ink remains intact after bone marrow (BM) transplantation, as illustrated by the highly decorated arm of a patient 2 yr after transplantation (bottom). (B) Schematic showing dendritic cell (DC)– and monocyte-related populations of the skin of mice and the maturation of melanophages from P4–5 macrophages after uptake of melanin or pigment. Inset illustrates the cycle of cell death and pigment recapture proposed by Baranska et al. Homologous populations of monocyte-derived cells and melanophages are also found­ in humans. LC, Langerhans cell.