The presence of the HTLV-I gene in peripheral blood mononuclear cells was studied by polymerase chain reaction in 42 patients including 16 with lung cancer, 12 with diffuse panbronchiolitis (DPB), 11 with idiopathic interstitial pneumonia (IIP), and 3 with pneumoconiosis and hematological malignancy. Sequences equal to a part of the pX gene were found in 44% of the lung cancer cases, 50% of the DPB cases, 55% of the IIP cases, and 100% of the cases of pneumoconiosis and leukemia. In the lung cancer cases, detection of the pX gene was frequently associated with the existence of diffuse interstitial pulmonary shadows. The pX gene was detected in 100% of patients with anti-HTLV-I antibody, 50% of patients with HTLV-I-related reaction and 14% of patients who tested seronegative. It may be inferred from the results that respiratory diseases that produce diffuse interstitial pulmonary shadows are closely associated with HTLV-I infection and that the HTLV-I-related reaction to the immunofluorescent test might reflect the latent infection state of HTLV-I.</p
