A novel in situ model to study Pneumocystis carinii adhesion to lung alveolar epithelial cells

• Published in: Journal of immunological methods Vol. 167; no. 1; pp. 161 - 171
• Main Authors: Pavia-Ruz, Noris, Ortega-Barria, Eduardo, Alroy, Joseph, Pereira, Miercio E.A.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 03.01.1994; Elsevier
• Subjects: AIDS/HIV; Animals; Antibodies, Fungal - pharmacology; Biological and medical sciences; Carbohydrates - pharmacology; Cell Adhesion - drug effects; Cell Adhesion - physiology; Cell interactions, adhesion; Cell Line; Fluorescein-5-isothiocyanate; Fundamental and applied biological sciences. Psychology; Glycoproteins - pharmacology; Histocytological Preparation Techniques; Humans; In situ model; Lectin; Lectins; Lung alveolar cell; Models, Biological; Molecular and cellular biology; Pneumocystis - cytology; Pneumocystis - immunology; Pneumocystis - physiology; Pneumocystis carinii; Pneumocystis carinii adhesion; Pulmonary Alveoli - cytology; Pulmonary Alveoli - physiology; Rats; Staining and Labeling; Lung alveolar cell; PBS; Lectin; EDTA; Pneumocystis carinii adhesion; GalNac; BSA; FITC; In situ model; Gal; TCA; Fuc; FCS; TIP; GlcNAc; TIIP; HBSS; PCP; BSM; Protozoa; Animal model; Rat; Lung; Rodentia; Pneumocystis carinii; Adhesion; Mechanism; In vivo; Vertebrata; Mammalia; Investigation method; Epithelial cell; Sporozoa
• ISSN: 0022-1759; 1872-7905
• DOI: 10.1016/0022-1759(94)90085-X

Pneumocystis carinii, an extracellular parasite thriving in the lungs of immunosuppressed mammals, is a major cause of death in AIDS patients in the USA. As a prelude to growth, the parasite adheres mostly to type I pneumocytes lining the alveolar spaces. The mechanism of adherence remains unknown, largely because of difficulties in isolating type I pneumocytes and maintaining them in vitro. As a first step to understand P. carinii adherence to its natural substrate, we developed an in situ method to directly study parasite binding to lung alveolar cells. We used formaldehyde-fixed paraffin-embedded sections of normal rat lung as substrate for adhesion. As in its binding to the lungs in vivo, P. carinni adhered preferentially to type I pneumocytes. Adherence was saturable, time and dose dependent, and selectively blocked by glycoconjugates, in particular bovine submaxillary mucin, fetuin, and asialofetuin, suggesting that it may be mediated by a lectin type of interaction. Further, IgG of rats with P. carinii pneumonia inhibited adherence, suggesting that it may react with parasite ligands involved in the recognition of type I cell receptors. Our results demonstrate the usefulness of the in situ model for studying the mechanisms of P. carinii adherence to alveolar cells. In addition, this method may be valuable for identifying neutralizing antibodies and drugs potentially useful for controlling the infection in vivo.