Neutralization of IL-6 activity by anti–IL-6R Ab or anti-gp130 Ab. To examine whether anti–IL-6R Ab or anti-gp130 Ab counteracted the biological effects of IL-6 on the cultured mast cells supported by SCF, each Ab was added at 5 μg/mL (▩) or 10 μg/mL (▪) to wells containing 1 × 10⁴ 10-week cultured cells with SCF, SCF+IL-6, or SCF+IL-4. SCF, 100 ng/mL; IL-6, 50 ng/mL; IL-4, 20 ng/mL. Significantly different from no Ab (*P< .0001).