IL9 and obesity due to melanocortin 4 receptor deficiency: Furthermore, in vivo macrophage depletion resulted in increased frequencies of ILC2s (Fig. 6F) and eosinophils (Fig. 6G) in the adipose tissue of HFD-fed IL-9R KO mice compared with PBS-treated controls, indicating that macrophages are the major target cell types of IL-9 during obesity.