FIG. 1.

PBMC or purified CD4⁺ cells were stimulated for 3 days with 3 μg of PHA per ml, washed, and subsequently passaged every 2 to 3 days by exchanging the entire amount of culture fluid with fresh culture medium. Purified CD8⁺ cells were obtained from PBMC stimulated with PHA for 3 days. On day 7 and thereafter, cells were replated at a density of 2 × 10⁶/ml. The concentration of chemokine in the cell culture fluids was measured by ELISA in duplicate (Quantikine; R&D Systems). The results show the maximal level of chemokines produced (adjusted per 10⁶ viable cells) as measured in cultured fluids on day 13. The data are representative of two to four different experiments.