Parasitic adherence and host responses in the development of Pneumocystis carinii pneumonia

Pneumocystis carinii pneumonia is a common cause of morbidity and mortality in patients with acquired immunodeficiency syndrome. In this article, the parasitic and host factors contributing to the pathophysiology of P carinii pneumonia will be reviewed. In particular, P carinii adherence to alveolar epithelial cells plays a central role in the development of pneumonia. Potential mechanisms mediating this attachment include cell surface glycoproteins, exogenous fibronectin and components of the parasitic cytoskeleton. Host factors contributing to respiratory impairment also have been recently evaluated. Inflammatory responses, aimed at ridding the lung of P carinii, may result in further deterioration of respiratory function. A better understanding of the host-parasite relationship in P carinii pneumonia eventually will lead to the development of novel therapies for this increasingly common respiratory disorder.