Immunohistochemistry of MC with an antibody against MCP-1. Purified human lung MC (A and B) and HMC-1 cells (C) were spun onto cytospin slides and stained with an antibody against MCP-1 (S101) as described in Materials and Methods. Primary lung MC were exposed to control medium (A) or rhSCF (B) for 2 hours before being exposed to S101. HMC-1 were used as untreated cells. Reactivity of lung MC with S101 was visualized by streptavidin-peroxidase and AEC and reactivity of HMC-1 cells with the antibody by alkaline phosphatase and neofuchsin (C). Note that expression of MCP-1 in lung MC was demonstrable after exposure to rhSCF, but not in control medium. Similar staining results were obtained when cells were exposed for 2 hours or 12 hours.