Figure 2.

Adipose tissue macrophages in mice with varying degrees of adiposity. Immunohistochemical detection of the macrophage-specific antigen F4/80 (black arrows) in perigonadal adipose tissue from C57BL/6J mice: (a) lean female, (b) Ay/⁺ female, (c) Lepob/ob female, (d) lean male, (e) DIO male, and (f) Lepob/ob male. Macrophages are stained brown. In lean animals (a and d), F4/80-expressing cells were uniformly small, dispersed, and rarely seen in aggregates. The fraction of F4/80-expressing cells was greater in moderately obese mice (b and e) and greatest in the severely obese Lepob/ob mice (c and f). Depots from all animals contained small, isolated F4/80 expressing cells (black arrows). In addition, depots from obese animals contained aggregates of F4/80 expressing cells (large blue arrows). Some macrophage aggregates contained small lipid-like droplets (small thin black arrow). Calibration mark = 40 μm.