Quantification of immune cells in full thickness and mucosal biopsies of the duodenum and rectum in a group of slaughter horses

Abstract

Background

Limited data are available on immune cells in the intestinal wall of healthy horses, hampering interpretation of results in case of disease.

Objectives

Characterize and quantify the immune cell populations and their distribution in duodenal and rectal biopsies of horses without gastrointestinal disease; compare immune cell counts (ICCTs) between full thickness- and mucosal biopsies.

Animals

Twenty horses fit for slaughter, slaughtered for meat production.

Materials and Methods

Full-thickness and endoscopic forceps obtained mucosal biopsies were taken within 30 min after slaughter from the duodenum and rectum. Samples were stained with hematoxylin and eosin (HE) and analyzed using immunohistochemistry (IHC). Immune cells were evaluated in epithelium, lamina propria and Brunner’s glands or submucosa. Differences between location and biopsy type were assessed using a generalized linear mixed effects model.

Results

Significantly more intraepithelial lymphocytes were found in duodenal full thickness biopsies (DFTs, median 9.0 epithelial lymphocytes/100 cells) compared to duodenal mucosal biopsies (DMs, median 5.35/100 cells, p = 0.002). Lymphocyte counts were significantly higher in the lamina propria of DFTs (median 7/0.01mm² ) compared to DMs (median 5/0.01mm^2, p < 0.001). Plasma cell counts were significantly higher in the lamina propria of DFTs (median 8.0/0.01mm²) compared to rectal full thickness and mucosal biopsies (median 4 and 3/0.01mm²). The combined number of B- and T-cells (IHC) in the duodenal lamina propria was higher than the number of lymphocytes (HE-stain, p < 0.001).

Conclusions

As ICCTs varied depending on location and biopsy type, separate reference values for both should be established. Immunohistochemistry facilitates identification of immune cells.