Lymphoglandular complexes of the normal colon: histochemistry and immunohistochemistry.

Abstract

LYMPHOGLANDULAR complexes (LGC) of the normal human colon have not been studied in detail hitherto and little is known of their structure, distribution or function. This study was undertaken to document synthetic properties of the epithelium of the LGC, the site and subset composition of their lymphocyte population and regional variations in these parameters that might exist within the normal large bowel. In the twenty-seven, macroscopically and microscopically normal colons examined, LGC epithelium produced the same types of mucin as colonic epithelium away from the lymphoid aggregates although the amounts of all mucin classes were considerably reduced. Secretory component production was the same in LGC epithelium as elsewhere. LGC in the ascending colon were larger and contained more lymphocytes (255±44 cells per high power field) than those in other anatomic regions (142±13; p<0.001). There was a greater ratio of B to T lymphocytes in LGC of the rectum (1.93±0.48) than in LGC of other regions (1.03±0.05; p<0.005). Rectal LGC also contained proportionately more T-suppressor cells than LGC elsewhere, the helper to suppressor ratio in these structures in the rectum being 2.25±0.31 against a mean ratio of 4.0±1.0 (p<0.0001) in LGC of other areas. The immunohistochemical findings in this study suggest that LGC contain precursors of the IgA producing plasma cells which ultimately populate the lamina propria of the intestinal mucosa. More lymphocytes were found in the lamina propria overlying the lymphoid aggregate of the LGC (38±5 cells per high power field) than in the lamina propria of the intervening mucosa (18±4; p<0.0001) although the subset ratios in both these areas was the same. In general, lymphocytes were no more frequent within the epithelium of the LGC (4±3 per 40 epithelial cells) than in other colonic epithelium, with the exception of certain rectal LGC, the epithelium of which contained raised numbers of lymphocytes (6±3; p<0.05).