31.   Immunocytochemistry in parallel sections showed that lysozyme mRNA was expressed only in macrophages or in metaplastic Paneth cells in longstanding inflammatory bowel disease.

32.   These results confirm increased macrophage activation in inflammatory bowel disease and suggest functional heterogeneity within the intestinal macrophage population.

33.   A disturbance in immunoregulatory control has long been suspected to play a major role in the pathogenesis of inflammatory bowel disease.

34.   Previous studies have shown morphological and histochemical heterogeneity of human intestinal macrophages, with a distinct population being prominent in inflammatory bowel disease.

35.   The signal intensity, evaluated by grain count, was stronger in inflammatory bowel disease, although the difference was again not significant.

36.   In colonic sections lysozyme mRNA expression was found in lamina propria macophages and, in five patients with longstanding inflammatory bowel disease, in metaplastic paneth cells.

37.   Another possibility is that the genetic regulation of the isotype response is different in the two populations of inflammatory bowel disease patients.

38.   We have therefore examined the IgG subclass pattern in rectal immunocytes and in serum of monozygotic twins with or without inflammatory bowel disease.

39.   Furthermore, this material offered an opportunity to study the IgG subclass pattern in inactive stages of inflammatory bowel disease because the affected twin were in clinical remission.

40.   Two more recently diagnosed monozygotic pairs with inflammatory bowel disease were also invited.