Adipose tissues display differential phagocytic and microbicidal activities depending on their localization

OBJECTIVE AND DESIGN: We recently reported that white preadipocytes phagocyte and kill micro-organ isms, suggesting an active involvement of fat cells in host defence. Since characteristics of adipose tissues vary according to their localization, we measured the phagocytic capacity of stromal-vascular fraction (SVF) cells from different pads of white and brown adipose tissue in primary culture. RESULTS: The microbicidal activities of SVF cells in inguinal and epididymal white depots were similar, but much higher than in brown fat pad. Considering the whole pad, the highest cytotoxic potential was found in inguinal white adipose tissue (WAT) depot, whereas interscapular brown adipose tissue (BAT) showed an extremely low ability to kill micro-organisms. These differences might be mainly attributed to preadipocyte activities, with regard to the low content in resident macrophages identified by their expression of F4/80 antigen. CONCLUSIONS: Taken together these results suggest that the role as macrophage-like cells for cells of the fat stroma-vascular fraction, among which preadipocytes, is not negligible. This emphasizes the relationship existing between inflammatory and adipose cells. A differential responsiveness of adipose pads to infections and inflammatory situations due to the specific phagocytic ability of their SVF cells was thus proposed.