关键词: 弓形虫, 小肠, 杯状细胞, 潘氏细胞, 巨噬细胞

Abstract:

Objective To examine the effect of acute Toxoplasma gondii infection on mucosal immune responses and immunopathology in mouse small intestines and unravel the mechanism. Methods Fifteen Kunming mice were randomly divided into two groups, including the T. gondii infection group (10 mice) and the control group (5 mice). Mice in the infection group were intraperitoneally injected with tachyzoites of the T. gondii RH strain (1 × 10³ tachyzoites per mouse), while animals in the control group were injected with an equal volume of PBS. Mice were sacrificed at 7 days post-infection, and the posterior section of small intestine (2 cm in length) and mesenteric lymph nodes were taken for paraffin embedding, preparing slices, and hematoxylin and eosin staining to observe the pathological changes of mice. The intestinal villi length and the crypt depth were measured, and the numbers of goblet cells and Paneth cells were counted. In addition, immunohistochemical staining was performed to count the number of CD68⁺ cells in small intestines. Differences of means were tested for statistical significance using independent sample t test with the software GraphPad Prism 10.1.2. Results The structures of mouse small intestinal villi and mesenteric lymph nodes were intact with a normal morphology in the control group, while mice in the infection group exhibited severe pathological damage in the small intestine, characterized by necrosis of villous epithelial cells, shedding or shortening of intestinal villi, deepening of intestinal crypts, and extensive infiltration of inflammatory cells in small intestinal mucosal tissues. Additionally, the histological structures of the mesenteric lymph nodes of mice in the infection group were disrupted, with diffuse necrotic lesions observed. T. gondii tachyzoites and pseudocysts were observed in mouse small intestines and mesenteric lymph nodes in the infection group. The mean length of mouse small intestinal villi was shorter in the infection group than that in the control group [(93.07 ± 2.158) μm vs. (125.0 ± 19.36) μm; t = 2.756, P < 0.05], and the mean depth of mouse small intestinal crypts was greater in the infection group than that in the control group [(49.04 ± 8.809) μm vs. (39.9 ± 4.174) μm; t = 2.382, P < 0.05]. The number of goblet cells per 10 mouse small intestinal villi was lower in the control group than that in the infection group [(78.70 ± 14.01) cells vs. (96.71 ± 13.89) cells; t = 2.618, P < 0.05], and the number of goblet cells per 10 mouse small intestinal crypts was fewer in the infection group than that in the control group [(31.60 ± 8.60) cells vs. (53.17 ± 13.03) cells; t = 4.014, P < 0.05]. The number of Paneth cells per 20 mouse small intestinal crypts was fewer in the infection group than that in the control group [(69.80 ± 8.90) cells vs. (103.0 ± 4.86) cells; t = 8.342, P < 0.01]. In addition, the number of CD68⁺ macrophages per high-power field in mouse small intestine tissue was larger in the infection group than that in the control group [(42.33 ± 11.41) cells vs. (15.75 ± 2.754) cells; t = 4.496, P < 0.01], and the number of CD68⁺ macrophages in mouse Peyer’s patches per high-power field was higher in the infection group than that in the control group [(185.0 ± 23.80) cells vs. (15.75 ± 2.754) cells; t = 9.286, P < 0.01]. Conclusion Acute T. gondii infection may induce small intestinal damage in mice, with a decrease in goblet cell and Paneth cell counts and an increase in CD68⁺ macrophage number in small intestinal tissues, suggesting that goblet cells, Paneth cells, and macrophages may contribute to mucosal immune responses and immunopathology of small intestines.

Key words: Toxoplasma gondii, Small intestine, Goblet cell, Paneth cell, Macrophage