In the context of obesity, the recruitment of circulating macrophages into AT is facilitated by two principal mechanisms: firstly, the secretion of chemokines, including MCP-1, C-C motif chemokine ligand 2 (CCL2), and leukotriene B4 (LTB4), by adipocytes as well as the stromal vascular (SV) component of adipose tissue [20]; secondly, through signals emanating from dying and stressed cells that are recognized by the NLRP3 and TLR-4, two pattern-recognition receptors (PRRs) on macrophages. The gene discussed is CCL2; the disease is obesity due to melanocortin 4 receptor deficiency.