CD80 and obesity due to melanocortin 4 receptor deficiency: Given that macrophage infiltration into adipose tissue is a hallmark of obesity (Bassaganya-Riera et al., 2009), tissue sections of eWAT from WT and Negr1−/− mice were prepared and stained with anti-F4/80 (pan-macrophage marker) and anti-CD80 (M1 macrophage marker) antibodies.