[594] Immunohistochemical Detection of IgG4 Plasma Cells in Lymphocytic and Collagenous Gastritis and Colitis

CE Aguilar, R Mertens, F Chung, HL Wang. Cedars-Sinai Medical Center, Los Angeles, CA

Background: Elevation of serum IgG4 level and increased number of IgG4-positive plasma cells in tissues have been reported in patients with autoimmune pancreatitis and other potentially autoimmune-mediated disorders, which often respond to steroid therapy. The current study was undertaken to determine whether IgG4-positive plasma cells were increased in lymphocytic and collagenous gastritis and colitis, conditions which are of unknown etiology.
Design: A total of 64 endoscopic biopsies with histologic diagnoses of lymphocytic gastritis (n=15), lymphocytic colitis (n=21), collagenous gastritis (n=5) and collagenous colitis (n=23) were immunohistochemically stained for IgG4 using a monoclonal antibody. The number of IgG4-positive plasma cells in the lamina propria in each case was determined by averaging the numbers identified in 3 high power fields (HPF) that showed highest concentrations of IgG4-positive cells.
Results: The number of IgG4-positive plasma cells per HPF ranged from 0-4 in lymphocytic gastritis (0.44±1.2), 0-6.3 in lymphocytic colitis (0.87±1.6), 0-40.3 in collagenous gastritis (10.1±17.3), and 0-5.7 in collagenous colitis (0.72±1.4). The mean numbers of IgG4-positive cells were not significantly different between lymphocytic gastritis and lymphocytic colitis (p=0.37) or between lymphocytic colitis and collagenous colitis (p=0.74). However, the mean numbers of IgG4-positive cells was significantly higher in collagenous gastritis in comparison to lymphocytic gastritis (p=0.034) or collagenous colitis (p=0.010). This difference was attributable mainly to 2 of the 5 cases of collagenous gastritis that showed a marked increase in the mean numbers of IgG4-positive cells (8.7 and 40.3, respectively). Only 1 case of lymphocytic colitis and 1 case of collagenous colitis showed a mean number >5 (6.3 and 5.7, respectively).
Conclusions: Tissue IgG4-positive plasma cells are sparse in general in lymphocytic and collagenous gastritis and colitis, arguing against an IgG4-related disease process in the majority of such cases. However, an increase in its number (>5 per HPF) is demonstrated in a small fraction of the cases (4/64), particularly in collagenous gastritis (2/5). Further study of a larger number of cases of collagenous gastritis is warranted.
Category: Gastrointestinal

Tuesday, March 23, 2010 9:15 AM

Platform Session: Section E, Tuesday Morning


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