IgG3 and IgG4 cells are increased in active ulcerative colitis

Cells containing various subclasses of IgG and IgA were counted in the rectal and colonic mucosae from 14 pediatric patients with ulcerative colitis (UC) and in rectal biopsy specimens from 10 control subjects using monoclonal antibodies and the peroxidase-staining method. In both the patients and controls, the IgG1 cells predominated. The numbers of IgG1, IgG2, IgG3 and IgG4 cells were highest in the colonic specimens of patients with UC. The numbers of IgG3- and IgG4-containing cells were increased in the rectal mucosa of untreated UC patients compared to controls. In the rectal mucosa of patients with UC, the percentage of IgG2 cells was decreased compared to the controls (20 vs. 28%; p less than 0.05). In the great majority (37 out of 40) of specimens the number of IgA1 cells was higher than that of IgA2. The median number of IgA1 cells in the rectal specimens of untreated patients was slightly higher than that in the rectal specimens of the controls, for IgA2 the numbers were similar. Accentuation of colorectal IgG3 and IgG4 responses may be characteristic early changes in UC.