IRF5 and obesity due to melanocortin 4 receptor deficiency: With the availability of Irf5 transgenic knockout mice, however, IRF5 has been also shown to play important roles in macrophage polarization, pain management, obesity, cardiovascular disease, systemic lupus erythematosus (SLE), arthritis and metabolic dysfunction19, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31.