Ultrastructural Demonstration of a Pore in the Cyst Wall of Pneumocystis Carinii

J Parasitol. 1994 Aug;80(4):644-8.


The proposed life cycle of the opportunistic organism Pneumocystis carinii (PC) includes the formation of a thick-walled cyst containing haploid progeny. The progeny cells mature within the cyst and are somehow released, leaving a collapsed empty cyst behind. Pneumocystis carinii cysts containing 8 intracystic bodies (ICB) as well as empty collapsed cysts have been commonly observed. In this study a single pore in the cyst walls of PC was observed by transmission electron microscopy in infected rat-lung preparations. Presence of a single pore in the cyst wall of an empty but noncollapsed cyst and in collapsed, empty cysts suggests that pore formation may be a mode of excystation for ICB of P. carinii.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Lung / parasitology
  • Male
  • Microscopy, Electron
  • Pneumocystis / ultrastructure*
  • Pneumonia, Pneumocystis / parasitology*
  • Rats
  • Rats, Sprague-Dawley