Immunocytochemical staining of tryptase and chymase in HCMCs cultured with or without IL-4. HCMCs grown in the presence of SCF (100 ng/mL) and IL-6 (80 ng/mL) for 10 weeks (defined as day 0 mast cells) were further cultured with or without IL-4 (10 ng/mL) in the presence of SCF and IL-6 for 56 days. Day 0 mast cells were stained with antitryptase (a), antichymase (b), subclass-matched control mouse IgG1 (c). Day 5 and day 56 mast cells cultured without IL-4 (d and f) or with IL-4 (e and g) stained with antichymase are shown. Typical chymase high positive mast cells (MC_TC^high; arrow head) and chymase low positive mast cells (MC_TC^low; arrow) are indicated (e). This experiment was repeated three times with similar results.