Increased immunoglobulin G4-positive plasma cells in collagenous sprue.

Collagenous sprue is a rare enteropathy whose etiology is unknown, but immune-mediated mechanisms are one of several possibilities. However, the role of immunoglobulin G4 (IgG4)-positive plasma cells has not been studied in collagenous sprue. Endoscopic biopsies from the duodenum with a histologic diagnosis of collagenous sprue (n = 40 from 35 patients), celiac disease (n = 25), peptic duodenitis (n = 15) and normal duodenum (n = 25) were immunohistochemically stained with IgG4 and CD138 antibodies. For each case, the quantities of IgG4- and CD138-positive plasma cells in the lamina propria were estimated by averaging the number in 3 high-power fields (hpf) that showed the highest concentration. Nine of forty collagenous sprue samples showed a mean of 10 or more IgG4 plasma cells per hpf, whereas none of the duodenal control biopsies showed 10 or more IgG4 plasma cells per hpf: celiac disease (P = .01), peptic duodenitis (P = .05), and normal duodenum (P = .01). Our study demonstrates that increased IgG4-positive plasma cells are present in a subset (23%) of collagenous sprue and may play a role in its pathogenesis.