Chlamydicidal activity of human alveolar macrophages.

Pneumonia due to Chlamydia trachomatis is a disease limited mainly to infants under 6 months of age. Rare cases have been reported in immunocompromised adults. One possible reason for the propensity of the pneumonia to occur in the very young may be related to differences in the phagocytic and bactericidal capacity of alveolar macrophages (AMs) in young infants and adults. At birth a function of AMs is clearance of surfactant-related material from the alveolar surface. Studies in animals have suggested that engorgement of AMs with surfactant-related lipids may reduce the microbicidal capacity of these cells. In the present study we determined that AMs obtained from healthy, nonsmoking adults were capable of killing both human biovars of C. trachomatis, with complete killing observed by 48 h after inoculation. Preincubation of AMs from adults with surfactant did not reduce the capacity of the cells to kill C. trachomatis.