P2RX4 and myalgic encephalomeyelitis/chronic fatigue syndrome: Light et al. reported increased leucocyte gene expression after moderate-intensity exercise in patients with CFS but not in matched healthy control participants, specifically for sensory (metabolite-detecting) receptors (e.g., ASIC3, P2RX4), adrenergic receptors (e.g., α-2A, B1, B2), and immune (e.g., IL-6, IL-10) genes (Light et al., 2012).