title: Attachment of Pneumocystis carinii to primary cultures of rat alveolar epithelial cells.
abstract: Pneumocystis carinii (PC) is an exclusively extracellular pathogen which causes pneumonia in immunocompromised individuals. Histologic studies have demonstrated that PC organisms attach preferentially to type I alveolar epithelial cells and rarely bind to type II cells. Previous reports have demonstrated that cultured type II cells develop a type I cell-like phenotype and express type I cell surface antigens. The current study examines the attachment of PC organisms to isolated rat type II alveolar epithelial cells as a function of time in culture. PC attachment to isolated type II cells increased as the type II cells differentiated in culture from 2.3 +/- 1.2% on Day 2 to 18.4 +/- 2.7% by Day 8. Previous studies have indicated a role for fibronectin (Fn) and Fn receptors as mediators of PC attachment. Addition of anti-Fn antibodies decreased attachment of PC to Day 8 type II cells from 19.4 +/- 2.5% to 9.4 +/- 1.9% (P < 0.01). Addition of antibodies to the alpha v and alpha 5 integrin subunits resulted in significant decreases in PC attachment to Day 8 type II cells. Examination of expression of alpha v and alpha 5 integrins on Day 2 and Day 8 type II cells demonstrated increased expression of both alpha v and alpha 5 integrin subunits on Day 8 type II cells. Overall these data indicate that attachment of PC to isolated rat type II cells increases as the cells differentiate into a type I cell-like phenotype in vitro and correlates with increased expression of Fn-binding integrins on the cell surface of the cultured type II cells.
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000502:physiology; D002448:Cell Adhesion; D002454:Cell Differentiation; D002478:Cells, Cultured; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism / Q000382:microbiology; D005353:Fibronectins / Q000502:physiology; D039482:Integrin alpha5; D039564:Integrin alphaV; D016023:Integrins / Q000096:biosynthesis / Q000502:physiology; D011010:Pneumocystis / Q000166:cytology*; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D051381:Rats; D017469:Receptors, Fibronectin / Q000502:physiology; D013997:Time Factors
chemical_list: D015703:Antigens, CD; D005353:Fibronectins; D039482:Integrin alpha5; D039564:Integrin alphaV; D016023:Integrins; D017469:Receptors, Fibronectin