Ultrastructural Changes in the Chlamydia-Infected Ileal Mucosa of Newborn Calves

Ultrastructural changes induced by chlamydial infection of mucosal cells of the ileum of newborn calves after oral inoculation were investigated. Depending on the stage of chlamydial development, the organelles of all infected cells became damaged. The damage was degenerative and included vesiculation of microvilli and swelling of the terminal web of absorptive epithelial cells. The mitochondria were swollen and had fragmented cristae. The endoplasmie reticulum was dilated and vesiculated, and infected cells gradually lost their ribosomes. The lateral junctional complex between infected cells became occasionally dislocated and fragmented. The basal lamina was thrown into folds, became discontinuous and separated from the basal border of the epithelial cells. The nuclei of infected cells were affected last, lost their chromatin pattern, and ultimately became pyknotic.