Local IgA subclass alterations in ulcerative colitis and Crohn's disease of the colon.

The subclass distribution of IgA producing cells was determined by paired immunofluorescence staining in colonic specimens from 10 patients with ulcerative colitis and eight with Crohn's disease. Compared with normal colonic mucosa, the percentage of IgA1 immunocytes showed a striking increase in both disorders. The proportion of mucosal IgA1 cells was significantly higher (p less than 0.05) in ulcerative colitis (median, 71.2%) than in Crohn colitis (median, 56.9%). Within each category of specimens no significant differences were noted between luminal and basal mucosal zones. The submucosal proportion of IgA1 cells was, however, significantly higher than the mucosal one in both ulcerative colitis (median, 89.1%; p less than 0.002) and Crohn colitis (median, 91.8%; p less than 0.005). The mucosal shift towards IgA1 production paralleled the magnitude of the submucosal IgA1 cell proportion in individual tissue samples. Taken together with the previously reported dramatic increase of local IgG production (particularly observed in the submucosa and basal parts of the mucosa), our findings indicated that there is an influx and/or proliferation of B cells representing systemic secondary immunity in the lesions of both diseases.