Abstract
The aim of this study was to detect the surface antigens in different stages of
experimental induced Pneumocystis carinii in Sprague-Dawley rats.
Immunohistochemical staining with monoclonal (900, 902 and 904) and polyclonal
(SP-D) antibodies demonstrated that the P. carinii organisms were mostly in the
alveolar lumina. The binding sites of the monoclonal (900, 902 and 904) and
polyclonal (SP-D) antibodies developed against P. carinii were examined at the
ultrastructural level by using a post-embedding immunogold labeling. The gold
particles were observed evenly on the surface of precyst and cyst stages of the
P. carinii. In the trophozoite stage, scattered gold particles were seen on the
pellicles and tubular expansions. The monoclonal antibodies reacted mainly with
pellicles of P. carinii, whereas SP-D labeled pellicles, intracystic bodies,
cytoplasms of alveolar macrophages, free floating surfactant material in the
alveolar spaces, and adjacent type II epithelial cells. In the immunogold
labeling, basically no significant differences were found in the precyst, cyst,
and ruptured cyst stages. These results indicate that the gold particles were
observed adhering to every stage of P. carinii, mostly concentrated on the
pellicles, and more concentrated in the precyst or cyst stage than trophozoite
stage which may be due to an increase in antigen accumulation during development
from the trophozoite to the cyst.