PBMCs from patients with smoldering/chronic ATL-manifested autocrine/paracrine cytokine-dependent spontaneous proliferation. (A) The 6-day spontaneous proliferation of ex vivo PBMCs was assayed on cells from smoldering/chronic ATL (n = 11, 9 smoldering ATL, 2 chronic ATL), acute-type ATL (n = 9), and normal donors (n = 20). (B) Spontaneous proliferation of smoldering/chronic ATL PBMCs (n = 11) was assayed in the presence of 10 μg/mL of monoclonal antibodies to IL-2 and IL-2R-α, IL-15 and IL-2/15R-β, IL-9 and IL-9R-α, and of a nonspecific control antibody (UPC10). (C) The spontaneous proliferation of PBMCs from a patient (patient 4) with smoldering/chronic ATL was assayed in the presence of 10 μg/mL monoclonal antibodies to IL-2, IL-9, IL-15, the combinations of anti-IL-2 with anti-IL-15, anti-IL-2 and anti-IL-9, and with a nonspecific control antibody (UPC10). This represents the data from 3 patients. (D) Spontaneous proliferation of PBMCs from 2 patients with acute ATL in the presence of 10 μg/mL monoclonal antibodies to IL-2 and IL-2R-α, IL-15 and IL-2/15R-β, IL-9 and IL-9R-α, and of a nonspecific control antibody (UPC10). The PBMCs proliferated at 23 262 and 28 569 cpm, respectively, without the addition of any antibody. The percentage inhibition was calculated by comparing the proliferation to that without any antibody.