Defect of In Vitro Digestive Ability of Polymorphonuclear Leukocytes in Paracoccidioidomycosis

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Abstract
Selected functions of polymorphonuclear leukocytes [PMN] were studied in patients with paracoccidioidomycosis (South American blastomycosis), in healthy control individuals and in patients with diseases unrelated to paracoccidioidomycosis. Patients with paracoccidioidomycosis were evaluated by standard immunological techniques. Phagocytosis and digestion of Paracoccidioides brasiliensis yeastlike cells in vitro was estimated by an original method. It was based on the appearance of phagocytosed P. basiliensis in preparations stained by a modification of the Papanicolaou method and examined with phase-contrast optics. Interpretation of such findings was confirmed by EM. Two strains of P. brasiliensis were used. Strain 8506 was freshly isolated from a patient. Strain Pb9 was non-pathogenic and had a peculiar cell wall composition. Yeast-like cells of the Pb9 strain were digested significantly better than those of strain 8506. A higher number of leukocytes/fungus cells led to a higher proportion of digested P. brasiliensis. Leukocytes from patients with paracoccidioidomycosis phagocytosed the fungus in a normal way but had a significant lower ability to digest it in vitro. When individual cases were analyzed, there was an excellent correlation between both of these and immunological parameters. Leukocytes from all groups behaved comparably in tests in general leukocyte function and in their abilities to kill and digest Candida albicans. As a group, PMN from patients with paracoccidioidomycosis apparently had a significant, rather specific, defect in their in vitro digestive capacity against phagocytosed P. brasiliensis. Their was an inverse correlation between strain pathogenicity and its susceptibility to in vitro digestion by PMN.