CD4 and obesity due to melanocortin 4 receptor deficiency: It is still unresolved as to which of the CD4+ and CD8+ T cells are the predominant T cells present in the adipose tissue of obese humans and animals and how obesity affects the balance within CD4+ T cells and among their different subpopulations, i.e., Th1, Th2, Th17, Treg, etc. The qualitative and quantitative changes in the immune cells present in adipose tissue are proposed to be key factors in the obesity-inflammation-metabolic disorder pathway.