No abstract

The fate of radiolabeled Aspergillus fumigatus galactomannan was studied after intravenous injection into rabbits and rats. At 1 hr, the liver contained 35% of the injected dose in rabbits and 30% in rats. Excretion of galactomannan into the urine, measured in rabbits, was another major catabolic route and accounted for 35% of the dose by 24 hr. Immunization of rabbits increased hepatic uptake and decreased urinary excretion. Hepatic uptake in unimmunized rats could be decreased by Saccharomyces cerevisiae mannan, alpha-methyl mannoside, and N-acetylglucosamine, known inhibitors of the macrophage mannose receptor. Autoradiography showed hepatic radiolabeled galactomannan to be concentrated in Kupffer cells, which express the mannosyl receptor for glycoproteins. Macrophage mannosyl receptors may constitute a general mechanism for clearing fungal mannans from the bloodstream.

No abstract

It has long been recognized that mast cells occur throughout connective tissues. Histologic studies have revealed that such cells release their granules into the surrounding environment upon exposure to both immunologic and nonimmunologic stimuli. By microscopy these extracellular granules appeared to be phagocytosed by fibroblasts and by blood-borne phagocytic cells as they entered the site of mast cell degranulation. Such in vivo observations led to the suggestion that mast cells both altered connective tissue components and influenced fibroblast function through these discharged granules. Recent in vitro studies using cultured fibroblasts and isolated mast cells and mast cell granules have confirmed both these hypotheses. In addition, such studies have also documented that fibroblasts degrade ingested mast cell granules. Such studies document that a number of critical interactions may occur between mast cells and connective tissue components.