Majority of interferon-γ-producing CD4⁺ cells in patients infected with human T cell lymphotrophic virus do not express Tax protein

The present study was conducted to determine whether interferon (IFN)-γ production by CD4⁺ cells in patients infected with human T cell lymphotropic virus (HTLV) is associated with expression of Tax, an HTLV type 1 (HTLV-1) transactivator. The frequency of IFN-γ production from CD4⁺ cells was greater in HTLV-1-infected patients (n = 21) than in uninfected (n = 3) and Strongyloides stercoralis-infected patients (n = 4), and greater in patients with HTLV-1 with detectable Tax than in patients with HTLV-1 with undetectable Tax. In the patients with HTLV-1 with detectable Tax, the majority of CD4⁺ cells making IFN-γ did not express Tax.