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京都大学0048新制・論文博士理学博士乙第3794号論理博第646号新制||理||303(附属図書館)6039UT51-54-H94(主査)教授 加藤 幹太, 教授 米田 満樹, 教授 日高 敏隆学位規則第5条第2項該当Kyoto UniversityDA

Insufficient interleukin-2 production from splenic CD4(+) T cells causes impaired cell proliferation and early apoptosis in SAMP1, a strain of senescence-accelerated mouse

We examined the proliferative and cytokine-producing activities of CD4(+) T cells from young mice of the senescence-accelerated mouse strain SAMP1, which had shown markedly low T-dependent antibody-producing responses. When splenic T cells were cultured with concanavalin A (Con A), the percentage of CD4(+) cells decreased earlier in SAMP1 than in C3H/He mice. At 40 hr of culture, the percentage of BrdU-labelled proliferating CD4(+) cells increased strongly in C3H/He, but only slightly in SAMP1. When purified CD4(+) T cells were cultured with Con A, the percentage of 5-bromo-2′-deoxyuridine (BrdU)-labelled cells peaked at around 48 hr of culture in both strains, but decreased significantly at 64 hr in SAMP1. The production of interleukin (IL)-2 but not IL-4 or interferon-γ (IFN-γ) was significantly lower in SAMP1 than in C3H/He at 48 hr of culture. IL-2 production was also markedly low in SAMP1, even under the stimulation of anti-CD3 with anti-CD28 antibodies. The frequency of cells producing IL-2 was significantly lower in SAMP1 than in C3H/He at 6–24 hr of culture with Con A. The percentage of annexin-positive and propidium iodide (PI)-negative apoptotic cells was significantly higher in SAMP1 than in C3H/He at 96 hr of culture. Exogenous IL-2 prevented the decrease in BrdU-labelled cells and the increase in apoptotic cells in the SAMP1 cell culture. These results indicate that SAMP1 CD4(+) T cells cannot produce IL-2 at levels sufficient to support cell proliferation and survival. This may account for the weak T-dependent antibody response in SAMP1 mice