CD4 and obesity due to melanocortin 4 receptor deficiency: Both ageing and obesity are tightly associated with “inflammaging” – a chronic low-grade inflammatory state characterized by inflammatory cytokine production and a dynamic reorganization of the adaptive immune compartment associated with co-emergence of exhausted T cells expressing inhibitory receptors including PD-1 and CD4+CD25highFoxP3+ regulatory T cells (60, 61).