FIG. 1.

BLV infection alters the survival of iPfB cells in short-term cultures. iPfB cells were cultured with OVK (control) or FLK (BLV) culture supernatant in medium alone or medium supplemented with 10 ng of recombinant human IL-2 and IL-4 (IL-2+4) per ml. For each experiment, triplicate cultures were established with 10 × 10⁶ cells/well, and cells from a single well were collected and analyzed at 2, 4, and 6 days p.i. (A) Viable-cell number was determined by counting total cell number with a Coulter particle counter and then determining the percent viable cells (propidium iodide exclusion) with a flow cytometer (FACScan). Incubation with BLV significantly (P < 0.05) increased viable-cell number in the presence (IL-2+4/BLV) but not in the absence (BLV) of recombinant human IL-2 and -4. (B) Sufficient viable cells were recovered from all treatment groups to assay spontaneous lymphocyte proliferation on days 2 and 4 p.i. A total of 2 × 10⁵ viable cells were plated in triplicate cultures, and cells were pulsed for 4 h with 0.4 μCi of [³H]thymidine per well. The level of spontaneous proliferation was not significantly different among treatment groups at the two time points assayed. Data presented are the mean + one SD of values from three experiments. ∗, P < 0.05.