The frequency of lymphocytic and reflux esophagitis in non-human primates.

We previously reported in humans a novel histologic phenotype of non-gastro-esophageal reflux disease called lymphocytic esophagitis. In this work, the esophagi of 121 non-human primates (103 baboons and 18 macaques) were investigated. 45 baboons (43.7%) and 9 macaques (50%) had lymphocytic esophagitis. The lymphocytic infiltration in the squamous epithelium involved not only papillary but also inter-papillary fields. Microscopic examination around the papillae revealed a mean of 52 intraepithelial lymphocytes (IELs) per high power field. Of the remaining baboons, 29 had reflux esophagitis (GERD). Among them, 25 (24.3%) 2 (1.9%) and 2 (1.9%) had grade1, 2 and 3 esophagitis, respectively. Of the remaining macaques, 4 had GERD: 1 (5.5%) with grade 1 and 3 (16.7%) with grade 2 esophagitis. None of the macaques had grade 3 esophagitis. The IEL population in lymphocytic esophagitis was composed of T cells, a subset of natural killer cells and of helper and inflammatory T cells. This investigation in non-human primates substantiates the identity of lymphocytic esophagitis as a subset of chronic esophagitis, as well as of reflux esophagitis. The antigenic agent(s) responsible for the marked immunological reaction in lymphocytic esophagitis in non-human primates (and in humans) remains unknown.