Intestinal macrophages are the largest group of mononuclear phagocytes in the body and play a role in intestinal innate immunity, neuroimmune interactions and maintaining intestinal homeostasis. Conversely, they also are implicated in numerous pathologies of the gastrointestinal tract, such as postoperative ileus and inflammatory bowel disease. As a result, macrophages could be potential therapeutic targets. To date, there are limited studies on the morphology and distribution of macrophages in the equine gastrointestinal tract (GIT). The aim of this study was to identify the location and abundance of resident macrophages in the equine GIT using CD163 as an immunohistochemical marker. Tissue samples were obtained post-mortem from 14 sites along the gastrointestinal tracts of 10 horses free from gastrointestinal disease; sample sites extended from the stomach to the small colon. CD163^+ve cells were present in all regions of the equine GIT from stomach to small colon. CD163^+ve cells were also identified in all tissue layers of the intestinal wall; namely, mucosa, submucosa, muscularis externa (ME), myenteric plexus and serosa. Consistent with a proposed function in regulation of intestinal motility, CD163^+ve cells were regularly distributed within the ME, with accumulations closely associated with the myenteric plexus and effector cells such as neurons and the interstitial cells of Cajal (ICC).

肠道巨噬细胞是体内最大的单核吞噬细胞群，在肠道先天免疫，神经免疫相互作用和维持肠道动态平衡中发挥作用。相反，它们也涉及胃肠道的许多病理学，例如术后肠梗阻和炎症性肠病。结果，巨噬细胞可能是潜在的治疗靶标。迄今为止，对马胃肠道（GIT）中巨噬细胞的形态和分布的研究很少。这项研究的目的是使用CD163作为免疫组织化学标记物鉴定马GIT中常驻巨噬细胞的位置和数量。死后从沿无胃肠道疾病的10匹马的胃肠道的14个部位获得组织样品。样本部位从胃部延伸到小结肠。CD163从胃到小结肠，马GIT的所有区域都存在^{+ ve}细胞。在肠壁的所有组织层中也发现了CD163 ^{+ ve}细胞。即粘膜，粘膜下层，外肌层（ME），肠神经丛和浆膜层。与拟议的肠道运动调节功能一致，CD163 ^{+ ve}细胞定期分布在ME中，其积累与肌间神经丛和效应细胞（如神经元和Cajal的间质细胞）紧密相关。