Immunocytochemical staining of uninfected MAC. By using IgG1 antibodies for negative control (isotype control), only an unspecific staining of the area of the nucleus of the cells was seen (A). With specific anti–IL-8 antibodies, intracellular IL-8 could be detected after 4 hours stimulation with LPS as granulated staining (B) and after 24 hours LPS as diffuse staining (C). After 4 hours stimulation with LPS, low amounts of IL-1β could be detected (D) and after 24 hours LPS, a strong specific staining was observed (E). Intracellular G-CSF could be detected in unstimulated cultures (F), as well as in LPS-stimulated cultures (G) (× 1,500).