Effect of CD8+ lymphocytes on the frequency of Tax expression in CD4+ lymphocytes.

(A) Peripheral blood mononuclear cells (PBMCs) were isolated from an asymptomatic carrier (HT) and cultivated for 24 hours either directly or after depletion of CD8+ or CD56+ lymphocytes, or both. The cells were then harvested and processed to perform the concomitant detection of Tax and CD4 antigens. One representative experiment of 3 is shown. (B) PBMCs were isolated from 3 asymptomatic carriers and from 3 patients with HTLV-I-associated myelopathy/tropical spastic paraparesis depleted of CD8+ cells and then cultivated for 24 hours after re-addition of a different number of autologous CD8+ cells. Tax positivity in CD4+ lymphocytes was then plotted as a function of the percentage of CD8+ lymphocytes in each culture. HTLV-I = human T-cell leukemia virus type I.