Pneumocystis carinii interactions with respiratory epithelium.

Ultrastructural studies indicate that the attachment of Pneumocystis carinii to alveolar epithelial cells is a central feature during development of this pneumonia. P. carinii attaches preferentially to type I alveolar epithelial cells, and rarely binds to type II cells. Extensive in vitro investigations support roles for both fibronectin and vitronectin, which bind to the organism, and mediate P. carinii attachment to respiratory epithelial cells through corresponding integrin receptors. Additional studies indicate that P. carinii cytoskeletal rearrangement occurs after initial binding of the organism to lung cells. Further, the attachment of P. carinii to host epithelial cells is believed to induce ultrastructural changes in these cells and to result in enhanced epithelial cell permeability. Further studies will be required to determine the mechanisms and consequences of P. carinii attachment to host epithelial cells in the intact host.