{'fraction_non_alphanumeric': 0.042467138523761376, 'fraction_numerical': 0.027300303336703743, 'mean_word_length': 4.409836065573771, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Change of cell-mediated cytotoxicity with aging.


 Evidence has been accumulating that both cellular and humoral immunocompetences progressively decline with aging in man (1, 2) as well as in experimental animals (3, 4).
 In a previous paper (5), we showed that the capacity of lymphoid cells from old C57BL/6J mice to induce graft-vs-host (GVH) reaction was reduced as compared to that from young mice. However, the proportions of θ.C 3H-bearing lymphocytes in the cell population of spleens and lymph nodes, and the indices of the response of lymph node cells to phytohemagglutinin showed little change with aging. In an extension of this observation, an attempt was made to elucidate the changes in cell-mediated cytotoxicity against allogeneic tumor cells with aging.
 Materials and Methods. Female inbred mouse strains C57BL/6J(H-2b) and DBA/2-(H-2d) were used throughout the experiment. C57BL/6J mice were either 1.5 to 2 or 15 to 20 months old, and DBA/2 mice 2 to four months old.