The in vitro interaction between yeast cells of Cryptococcus neoformans and Lewis rat alveolar macrophages (AM phi) was studied in the absence of serum. AM phi were harvested by lung lavage, and monolayers of adherent cells were established in wells of microtiter plates. Radiolabeled yeast cells were added to fresh AM phi monolayers, the plates were incubated at 37 degrees C under 5% CO2, nonadherent yeasts were removed, and phagocytosis (i.e., attachment or ingestion) was determined by measuring adherent radioactivity. AM phi were able to bind or ingest, and kill, encapsulated strains of C. neoformans in the absence of serum. Serum-free phagocytosis was suboptimal by comparison with phagocytosis in the presence of serum. The mechanism of serum-free phagocytosis involves a receptor on the AM phi with affinity for mannose-rich determinants present on the yeast cell walls and unrelated to the capsular polysaccharide. Opsonin-independent phagocytosis was only detected with nonencapsulated, small, and medium encapsulated strains of C. neoformans. Large encapsulated strains were not taken up without serum. Serum-free phagocytosis could be of critical importance in the alveolar spaces, where only marginal concentrations of serum opsonins are initially present.

The fruit-eating bat, Artibeus lituratus, was fed known quantities of viable yeast cells and mycelial particles of Paracoccidioides brasiliensis in an attempt to assess the role of this animal in the distribution of this agent in nature. Results of mycosal cultures of the stomach, upper intestine, lower intestine and rectum clearly showed that the fungal cells were unable to survive more than 8 hours in the digestive tract of the bat. The mycelial particles were more susceptible than the yeast and were killed before passing to the rectum. The fungus died rapidly in the voided fecal material. These findings indicate the improbability of isolating P. brasiliensis from the digestive tract of wild captured bats and show that A. lituratus probably plays no role in the distribution of this fungus in nature.

Guinea pig pulmonary macrophages phagocytized but did not kill nonencapsulated cells of Cryptococcus neoformans. The phagocytic process was inhibited by cryptococcal capsular polysaccharide. Pulmonary macrophages, activated by preinjecting heat-killed bacteria into intact animals, did not kill the engulfed yeast cells. Labeled cells of C. neoformans were neither killed nor cleared from guinea pig lungs 6 h postexposure. The results of our experiments indicate that during the first few hours after the lung is exposed to the infectious particle of C. neoformans the pulmonary macrophage does not function primarily to kill engulfed yeast cells. We believe that a rapid yet transient acute inflammatory response probably plays a major role in this process during the first few hours after C. neoformans enters the lung.

Schizophyllum commune, a basidiomycete, has been shown to be pathogenic for normal white Swiss mice inoculated intraperitoneally. Deaths occurred in suckling mice; weanling mice were more susceptible to infection than adults. Treatment with either cortisone or mucin or both did not alter the infection in adult mice, but cortisone did render the weanling mice much more susceptible, causing deaths in 75%. The fungus, isolated from human tissue, was shown to invade the lungs, lymph nodes, liver and subcutaneous tissue, producing subacute to granulomatous lesions. Cultures from these tissues were repeatedly positive and tissue sections showed penetration of the parenchyma by hyphae possessing clamp connections and sterigmata-like excretory organelles.

Schizophyllum commune, a basidiomycete, has been shown to be pathogenic for normal white Swiss mice inoculated intraperitoneally. Deaths occurred in suckling mice; weanling mice were more susceptible to infection than adults. Treatment with either cortisone or mucin or both did not alter the infection in adult mice, but cortisone did render the weanling mice much more susceptible, causing deaths in 75%. The fungus, isolated from human tissue, was shown to invade the lungs, lymph nodes, liver and subcutaneous tissue, producing subacute to granulomatous lesions. Cultures from these tissues were repeatedly positive and tissue sections showed penetration of the parenchyma by hyphae possessing clamp connections and sterigmata-like excretory organelles. El Schizopyllum commune es un basidiomiceto que ha demostrado ser patogénico para los ratones blancos por inoculación del IP. Ocurrieron muertes en ratones lactantes y los destetados fueron mas susceptibles a la infección que los adultos. El tratamiento con cortisona y/o con mucina no alteró la infección en los adultos pero la cortisona hizo que los destetados fueran mucho más susceptibles causando muertes en un 75% de ellos. El hongo, aislado del tejido humano, ha demostrado invadir los pulmones, los nódulos linfáticos, el hígado y tejidos subcutáneos produciendo lesiones, desde subagudas hasta granulomatosas. Los cultivos de estos tejidos fueron repetidamente positivos y los cortes de tejido demostraron penetración del parénquima por hifas que tienen “clamp connections” y órganos excretorios semejantes a las esterigmatas.