[The defensive role of human pulmonary alveolar macrophages and polymorphonuclear leukocytes against a strongly or weakly virulent strains of Cryptococcus neoformans].

The phagocytic and killing activities of human pulmonary alveolar macrophages (PAM) and polymorphonuclear leukocytes (PMN), and superoxide (O2-) production in phagocytizing PAM and PMN were studied by using a strongly and weakly virulent strains of Cryptococcus neoformans (C. neoformans) in mice. The strongly virulent strain was encapsulated with a thick capsule while the other had a thin one. The phagocytic and killing activities of PAM and PMN against the strongly virulent strain were lower than against the weakly virulent one. There was no significant difference between PAM and PMN in terms of phagocytic or killing activities and O2- production. It seems likely that O2- plays no defensive role in the intracellular killing of C. neoformans by PAM and PMN because no correlation was found between the killing activity and O2- production. These results indicate that human PAM and PMN play an effective role in host defense against the weakly virulent strain of C. neoformans encapsulated with a thin capsule but are not effective against the strongly virulent strain encapsulated with a thick capsule.