Spontaneous MIP-1β and MIP-1α production from ATL cells. The cytokine levels in culture supernatants (a and c) collected from normal CD4⁺ T cells (group A) and the ATL cells (group B) after 24 hours of incubation at 37°C without any stimulation or cytosol (b and d) of normal CD4⁺ T cells (group A) and ATL cells freshly obtained from peripheral blood of ATL patients (group B) were determined by MIP-1β (a and b) and MIP-1α (c and d) ELISA system. Each point represents the concentration of MIP-1β and MIP-1α in the lysate or supernatant derived from 1 × 10⁵ cells of individual subjects. Bars represent the mean ± SD of each group (Student's t-test).