Quantification of immune cells in full thickness and mucosal biopsies of the duodenum and rectum in a group of slaughter horses.
Authors: Robel M, Grest P, Riond B, Zablotski Y, Schoster A
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Establishing baseline immune cell distributions in healthy equine intestinal tissue is essential for diagnosing inflammatory bowel conditions, yet reference ranges remain poorly defined. Robel and colleagues collected full-thickness and endoscopic mucosal biopsies from the duodenum and rectum of 20 slaughter horses within 30 minutes of death, then quantified immune cell populations using haematoxylin and eosin staining and immunohistochemistry across the epithelium, lamina propria, and deeper glandular layers. The duodenum contained substantially higher intraepithelial lymphocytes in full-thickness samples (median 9.0 per 100 cells) than mucosal biopsies alone (5.35 per 100 cells), and plasma cell counts in the duodenal lamina propria were markedly elevated compared to rectal tissue. Critically, immunohistochemistry revealed significantly greater B- and T-cell populations in the duodenal lamina propria than routine histological staining could identify, suggesting standard HE staining underestimates immune cellularity. Clinicians should recognise that biopsy type and anatomical location substantially alter immune cell interpretation; mucosal pinch biopsies may miss deeper inflammatory changes, and separate reference intervals are now required to avoid misclassifying healthy tissue as pathological or overlooking genuine disease.
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Practical Takeaways
- •When interpreting intestinal biopsies for immune cell status, always consider whether the sample is full-thickness or mucosal and from which anatomical site (duodenum vs rectum), as this significantly affects cell counts
- •Immunohistochemistry is superior to routine staining for accurately identifying and quantifying specific immune cell populations in equine intestinal tissue
- •Establish location- and biopsy-type-specific reference ranges before comparing individual patient samples to baseline values for disease diagnosis
Key Findings
- •Duodenal full-thickness biopsies contained significantly more intraepithelial lymphocytes (9.0/100 cells) compared to mucosal biopsies (5.35/100 cells, p=0.002)
- •Lymphocyte and plasma cell counts in the lamina propria were significantly higher in duodenal full-thickness biopsies than mucosal biopsies
- •Immunohistochemistry identified more combined B- and T-cells in duodenal lamina propria than hematoxylin and eosin staining alone
- •Immune cell counts vary significantly by anatomical location and biopsy type, requiring separate reference values for clinical interpretation