In the three epithelial cell types (human nasal epithelial cells, immortalized CF1-16 cell line, and CF bronchial epithelial cells), the ED50 for serum was 5, 5, and 3% with extrapolated maximums of 2.3, 2.8, and 24 ng/mL of IL-8, respectively. The gene discussed is CXCL8; the disease is cystic fibrosis.