Significantly lower levels of IL-4 (p = 0.04, 0.02, 0.01) and IL-8 (p = 0.02, 0.00, 0.01) were observed in female CFS subjects compared to their GWI counterparts at all three phases of exercise. This evidence concerns the gene CXCL8 and myalgic encephalomeyelitis/chronic fatigue syndrome.