IL33 and obesity due to melanocortin 4 receptor deficiency: Elevations in fatty acids in the lungs of db/db mice (Fig 3) would also be expected to increase the ability of ILC2s to produce type 2 cytokines [66], and we have reported that IL-33 causes ILC2 activation and type 2 cytokine release are important for obesity-related increases in the response to O3[16,17].