Lymphocytic and collagenous colitis: an immunohistochemical study

Area of Science:

• Gastroenterology
• Immunology
• Colorectal Pathology

Background:

• Lymphocytic colitis (LC) and collagenous colitis (CC) share increased intraepithelial lymphocytes (IELs).
• Similarities suggest a potential common underlying immune mechanism.
• Investigating IEL and lamina propria lymphocyte phenotypes is crucial.

Purpose of the Study:

• To determine the phenotype of IELs and lamina propria lymphocytes in LC and CC.
• To compare immune cell profiles between LC, CC, and controls.
• To elucidate potential shared pathogenic pathways.

Main Methods:

• Immunohistochemical analysis of colonic and ileal biopsies from LC, CC, and control groups.
• Utilized monoclonal antibodies targeting T-cells (CD4, CD8), HLA DR, and T-cell receptor (TcR) variants (alpha beta, gamma delta).
• Examined IELs and lamina propria lymphocytes across all bowel segments.

Main Results:

• Both LC and CC showed increased IEL counts, with a predominance of CD 8 IELs over CD 4 IELs.
• Most IELs expressed TcR alpha beta; TcR gamma delta-bearing cells were not elevated.
• CD 4+ helper T-cells were predominant in the lamina propria, and epithelial cells abnormally expressed HLA DR antigens.

Conclusions:

• Immune abnormalities in LC and CC are similar, pointing to a potential MHC-restricted immune mechanism.
• Evidence includes CD 4+ T-cell accumulation, CD 8 TcR alpha beta IEL-related epithelial damage, and abnormal HLA DR expression.
• The immune mechanisms in LC/CC likely differ from those in celiac disease.