Neutrophils, eosinophils, and mast cells in the intestinal wall of dogs naturally infected with Leishmania infantum

Abstract Visceral leishmaniasis (VL) is a disease caused by the protozoa Leishmania infantum and can cause an inflammatory reaction in the gastrointestinal tract, however the role of granulocytic cells (neutrophils, eosinophils, and mast cells) in the intestine of dogs infected is not fully understood. We performed a quantitative analysis these cells in the intestinal wall of dogs with canine visceral leishmaniasis (CVL). Twenty dogs were assigned to one of three groups: group 1 (G1, n=8), dogs with CVL and L. infantum amastigotes in the intestine; group 2 (G2, n=9), dogs with CVL but without intestinal amastigotes; and group 3 (G3, n=3), uninfected dogs (control group). Granulocytic cells were counted in the crypt-villus unit (mucosa), submucosa, and muscle layer of the intestinal mucosa. Cell counts were higher in the intestinal wall of dogs from G2 followed by G1 and G3 (p≤0.05). In G1, there was a low inverse correlation between parasite burden of the small intestine and granulocyte counts (r= -0.1, p≤0.01). However, in G2 dogs, mast cell and eosinophil numbers showed positive correlation (r=0.85, p≤0.01). The granulocytic cell hyperplasia observed in the intestine of L. infantum-infected dogs suggests that these cells may be involved in the cell-mediated immune response for parasite elimination.

摘要 内脏利什曼病（Visceral leishmaniasis, VL）是由婴儿利什曼原虫（Leishmania infantum）引发的疾病，可引发胃肠道炎症反应，但受感染犬肠道内粒细胞（granulocytic cells，包括中性粒细胞（neutrophils）、嗜酸性粒细胞（eosinophils）与肥大细胞（mast cells））的作用尚未完全阐明。本研究对犬内脏利什曼病（canine visceral leishmaniasis, CVL）患犬的肠壁粒细胞开展了定量分析。将20只试验犬分为3组：第1组（G1，n=8）为肠内检出婴儿利什曼原虫无鞭毛体（amastigotes）的CVL患犬；第2组（G2，n=9）为未检出肠道无鞭毛体的CVL患犬；第3组（G3，n=3）为未感染的健康犬（对照组）。研究人员分别对肠黏膜隐窝绒毛单位（crypt-villus unit，黏膜层）、黏膜下层（submucosa）及肌层（muscle layer）内的粒细胞进行了计数。结果显示，G2组患犬肠壁的粒细胞计数最高，其次为G1组与G3组（p≤0.05）。G1组患犬的小肠寄生虫负荷（parasite burden）与粒细胞计数呈低度负相关（r=-0.1，p≤0.01）。而G2组患犬的肥大细胞与嗜酸性粒细胞数量呈显著正相关（r=0.85，p≤0.01）。本研究观察到感染婴儿利什曼原虫的犬肠道出现的粒细胞增生现象，提示这类细胞可能参与了清除寄生虫的细胞介导免疫应答（cell-mediated immune response）。