Sequential histologic changes in the healing process in small bowel allografts treated for acute cellular rejection

Area of Science:

• Gastroenterology
• Transplant Surgery
• Pathology

Background:

• Acute cellular rejection (ACR) is a frequent complication following small intestinal transplantation.
• Assessing treatment response in ACR requires understanding the temporal resolution of biopsy findings.
• Pathologists need to differentiate between resolving and ongoing rejection in follow-up biopsies.

Purpose of the Study:

• To determine the sequence and timing of resolution for key histologic features of acute cellular rejection after treatment in small intestinal transplant recipients.
• To provide guidance for pathologists evaluating follow-up biopsies for ACR treatment efficacy.

Main Methods:

• Retrospective review of 16 small intestinal transplant cases with diagnosed ACR and subsequent biopsies.
• Evaluation of epithelial injury, lamina propria inflammation, and crypt apoptotic bodies in biopsies before and after treatment.
• Comparison with age-matched control biopsies.

Main Results:

• Epithelial injury (mucin depletion) resolved by 2 weeks post-treatment.
• Lamina propria inflammation significantly decreased by 1 week and normalized by 3 weeks.
• Apoptosis levels fell below the rejection threshold by 2 weeks and reached control levels by 3 weeks.

Conclusions:

• The resolution of histologic ACR features follows a predictable timeline after therapy.
• Reduced epithelial injury and lamina propria inflammation are evident within 1 week of treatment.
• Persistent findings may indicate ongoing rejection, aiding in patient management.