The results of the evaluation of the presence of the p75NTR Ser205Leu polymorphism, viral load, and cytokine levels in asymptomatic individuals suggested that the polymorphism may induce higher levels of TNF-α, which would contribute to the control of infection, leading to a lower viral load without promoting a marked inflammatory response (individuals with the Ser/Leu genotype had lower levels of IL-10); this is different from what was observed in patients with symptoms related to HTLV-1 infection, who had higher levels of TNF-α and IL-10 and a high proviral load. The gene discussed is IL10; the disease is infection.