Morphologic and biochemical studies of chitin expression in Pneumocystis carinii.

Tomato lectin, which binds oligosaccharides of N-acetyl-D-glucosamine, and an antiserum against macromolecular chitin were used to probe sections of human and murine lungs infected with Pneumocystis carinii. By light, fluorescence and electron microscopy, lectin and antiserum binding patterns indicated that both human and murine strains of P. carinii express chitin at all identifiable stages of their life cycles. Light microscopic autoradiographs of murine P. carinii cultured in vitro with 3H-glucosamine revealed dense incorporation of the radiolabel into the cell walls in a pattern analogous to those of the antiserum and lectin binding studies. These investigations offer further evidence that chitin is an integral part of the cell wall of P. carinii trophozoites and cysts.