Differential antimicrobial activity of human mononuclear phagocytes against the human biovars of Chlamydia trachomatis.

The antimicrobial activities of human mononuclear phagocytes against Chlamydia trachomatis were investigated. Phagocytes cultured for 7 days or less were efficiently microbicidal. Almost complete inactivation of organisms from both human biovars was observed after 48 hr of incubation. However, organisms from the lymphogranuloma venereum (LGV) biovar survived in mononuclear phagocytes infected after 8 days or more in culture, whereas those from the trachoma biovar continued to be killed by such cells. Phagocytes cultured as long as 21 days killed the trachoma organisms with the same effectiveness as those cultured for 7 days or less. An ultrastructural study of inoculated phagocytes illustrated phagolysosomal fusion with degradation of organisms from either biovar in phagocytes which had been cultured for 24 hr before infection. Phagolysosomal fusion was not observed in cells which had been cultured for 8 days or more and then infected with LGV. The addition of interferon-gamma to these macrophages partially restored the phagocytes' microbicidal activity for LGV. Furthermore, a synergistic effect was observed when eosinophil peroxidase was added with interferon. Specific antibody failed to neutralize the infectivity of LGV organisms in 8-day or older mononuclear phagocytes. The findings may reflect the differences in disease syndromes between the two biovars, with the trachoma biovar causing more peripheral diseases and the LGV biovar causing a more systemic disease, with lymph node involvement as its main syndrome.