HISTOPATHOLOGICAL STUDIES OF SPOROTHRIX-SCHENCKII-INOCULATED MICE - POSSIBLE FUNCTIONS OF POLYMORPHONUCLEAR LEUKOCYTES IN NORMAL AND IMMUNOCOMPROMISED (CONGENITALLY ATHYMIC NUDE) MICE

Defense mechanisms against Sporothrix schenckii were studied using mou se models. After an intracutaneous injection of the yeast form of S. s chenckii to the dorsal skin of the congenitally athymic nude and norma l heterozygote littermate mice, nodules were formed. They regressed an d disappeared in 10 weeks in the case of normal mice. On the other han d, nodules and then ulceration developed progressively in nude mice un til all animals expired by dissemination of microorganisms at the 11th week of inoculation. Histopathologically the migrated cells were simi lar in both the normal and the nude mice, particularly during the earl y phase (within 24 h), with infiltration by PMNs being predominant. Fr agmentation of S. schenckii commenced early during the 12-24 h stage o f inoculation in the normal mice, while such fragmentation was scarce in nude mice even though numerous PMNs accumulated. Microscopic observ ations in the early stages (within 24 h of inoculation) suggested that the lack of killing activity by PMNs in nude mice contributes more to the impaired defense than the lack of macrophage activation by T-cell s.