Cytokine release by ovine macrophages following infection with Chlamydia psittaci

Chlamydia psittaci is an obligate intracellular pathogen that causes aborti on in both sheep and humans. The disease in sheep (but not humans) is chara cterized by a long-term persistent phase that appears to be under the contr ol of interferon-gamma. However, nothing is known about cytokine induction that precedes the persistent phase in sheep. Primary alveolar lavage cells recovered from normal adult sheep were used to study cytokine production in the first 72 h of infection with C. psittaci. These cells were phenotypica lly characteristic of macrophages, being adherent, phagocytic, CD14(+) and staining positive for non-specific esterase. In vitro infection of the macr ophages with C. psittaci resulted in the release of IL-1 beta, IL-8 and gra nulocyte-macrophage colony-stimulating factor (GM-CSF) as measured by ovine specific ELISAs. Heat-treated chlamydiae (1 h at 65 degrees C) did not ind uce the release of IL-1 beta, but the release of IL-8 was similar to that i nduced by untreated organisms. The cells from different sheep varied most n otably in their patterns of GM-CSF release in response to heat-treated and untreated organisms.