Morphologic and cell kinetic investigations of the spleen after repeated in situ freezing of liver and kidney.

In order to evaluate a possible primary or secondary immunologic response of the spleen after single or repeated in situ freezing of parenchymal organs such as liver and kidney within a four week period, light microscopic and cell kinetic investigations with tritiated thymidine were performed on spleens of non-germfree rats. Sham operations served as controls. The sham operations did not induce any significant morphological or cell kinetic changes in the splenic white pulp. After cryolesions were produced in the liver and kidney, the percentages of activated germinal centers, labeled germinal center cells, and cells in the perifollicular area of the lymphatic mantle and marginal zones increased, with maxima during the first 3 days. The investigations show that the cellular reaction of the spleen starts earlier and is more prominent after repeated in situ freezing than after a single cryolesion. These findings point to an immunologic response of the anamnestic type, and correspond to results after repeated freezing of normal and malignant tissue of the urogenital tract. These cell kinetic results are important in the evaluation of further immunologic studies involving the cryotherapy of malignant tissues.