Lymphotoxin inhibits Chlamydia pneumoniae growth in HEp-2 cells

Cytokines such as gamma interferon and tumor necrosis factor alpha (TNF-alp ha) inhibit the intracellular replication of Chlamydia pneumoniae or Chlamy dia trachomatis. In this study, we found that another cytokine, lymphotoxin (TNF-beta), restricts the growth of C. pneumoniae in HEp-2 cells. When lym photoxin (10 U/ml) was added during incubation from 8 to 16 h postinoculati on, inclusion body formation was severely reduced. In addition, we observed activation of nitric oxide production and the nuclear transition of NF-kap pa B in HEp-2 cells in response to lymphotoxin. These results suggest that inhibition of chlamydial growth by lymphotoxin is mediated, at least in par t, by nuclear transition of NF-kappa B, resulting in induction of nitric ox ide synthase to produce nitric oxide, a potent bacteristatic agent. This is the first report on antichlamydial activity of lymphotoxin through inducti on of nitric oxide.