Influence of human T lymphotrophic virus type I on diffuse pan‐bronchiolitis

SUMMARY Human T lymphotrophic virus type‐I (HTLV‐I), a human retrovirus, infects CD4 + lymphocytes and is thought to modify their function and a possible association with pulmonary diseases has also been suggested. However, little is known about the influence of HTLV‐I on diffuse pan‐bronchiolitis (DPB), a chronic inflammatory lung disease with infiltration of lymphocytes and hyperplasia of the bronchus‐associated lymphoid tissue. In this study, 35 DPB patients with and without HTLV‐I infection were examined. HTLV‐I positive DPB patients were likely to have a larger affected area with lower FEV 1 . The CD3 + /CD25 + lymphocyte percentage was significantly higher in the BALF of HTLV‐I positive patients than in negative patients. MIP‐1 α , IP‐10 and levels in BALF were also significantly higher in HTLV‐I positive patients than in negative patients. The levels of MCP‐1 and IL‐8 were not significantly different. In HTLV‐I positive patients, the MIP‐1 α and IP‐10 levels showed a significant positive correlation with the percentage of CD3 + /CD25 lymphocytes. BALF cells of all HTLV‐I positive DPB patients showed expression of p40 tax mRNA. We suggest that HTLV‐I infection may modify DPB pathogenesis via activation of T cells. We also found that the frequency of ATL development in HTLV‐I positive DPB patients was significantly higher than in all HTLV‐I positive patients (OR = 8·22, 95% CI = 2·61–25·9, P  < 0·01). The levels of TGF‐ β in patients who developed ATL were significantly lower than in patients who did not develop ATL. Sensitivity and specificity were 80% and 85·7%, respectively (cut‐off = 20 pg/ml). We also propose that these features should be taken into consideration in the treatment of DPB in HTLV‐I infected individuals.