Ultrastructural analysis of the anti-chlamydial activity of recombinant murine interferon-gamma

The effect of murine interferon-gamma (MuIFN-gamma) on the developmental cycle of Chlamydia trachomatis in McCoy cells was analyzed by light and electron microscopy. Addition to the culture media of 10 ng/ml of MuIFN-gamma, either 24 hr before or immediately after Chlamydia infection, resulted in a significant inhibition of the growth of this organism. Microscopic analysis showed that with both treatments the majority of microorganisms were arrested at the elementary body stage. Only a few small chlamydial inclusions were detected at 48 hr postinfection and contained predominately reticulate bodies. Furthermore, the growth of Chlamydia was arrested in cells that were treated with MuIFN-gamma at various intervals following infection. Addition of MuIFN-gamma at 8 or 12 hr after infection resulted in the arrest of chlamydial growth before initiation of reticulate body fission. When the MuIFN-gamma was added 24 hr postinfection, we could detect, by electron microscopy, inhibition at the stage of reticulate body replication.