Increased resistance of splenectomized mice to Sporothrix schenckii infection

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Abstract
The susceptibility of splenectomized mice to Sporothrix schenckii was studied, and the role of the spleen in the host defense is discussed. S. schenckii Sp-1 and ddy male mice were used. The mice were divided into 3 groups consisting of splenectomized, sham-operated and intact mice. Each mouse was inoculated intravenously with 2×106 yeast cells 7 days after operation and the mice were sacrified at adequate intervals for 30 days. Then histological sections stained with H&E or by PAS were prepared from various visceral organs. Using the liver sections the number of yeast cells in a 40 mm2 was counted. Furthermore, the colony forming unit in 100 mg of the liver tissue was compared to each other. In the sham-operated and intact mice many purulent lesions appeared on the 5th day. On the 8th day mononuclear cells accumulated at the foci, and on the 10th day most of the foci became granulomatous. The number of yeast cells in granulomatous lesions reached a peak on the 10th day and thereafter decreased abruptly. On the other hand, in the splenectomized mice approximately half of foci became granulomatous on the 5th day, and the number of yeast cells in the foci began to decrease after the 5th day. There were definite differences in the colony forming unit between the splenectomized and sham-operated or intact mice sacrificed 9 days after inoculation. The colony forming unit of the former is 9.3×105 on the average, while that of the latter two is 5.6×106 and 5.1×106 on the average, respectively. In conclusion the resistance of ddy mice to S. Schenckii infection is enhanced due to splenectomy.