In-vivo encapsulation and killing of Litomosoides carinii in white rats.

Ultrastructural studies revealed that in albino rats Litomosoides carinii was encapsulated and eventually killed in the pleural cavity by adherent host cells. Encapsulation was an organized cellular reaction which sequestered and eventually degraded the parasites. The process evolved in three phases: primary accumulation of host cells, especially eosinophils and macrophages, around the parasites with concentration of eosinophils on the parasite surface; secondary transformation of macrophages into epithelioid cells which replaced eosinophils on the parasite surface; finally, dead parasites became calcified and were gradually degraded within a tough, compacted fibrotic capsule.