Immunoglobulins and IgG subclasses in patients with inflammatory bowel disease

Serum immunoglobulin levels and distribution are altered in patients with inflammatory bowel disease (IBD). The purpose of this study is to examine the value of serum concentration of IgG subclasses for the diagnosis and evaluation of disease activity of IBD and to assess possible differences in the immunoglobulin changes between patients with Crohn's disease (CD) and ulcerative colitis (UC).

We measured serum IgG and IgG subclasses concentrations as well as IgA, IgM, ESR, CRP, elastase levels and granulocyte count of 96 patients with chronic IBD (69 with CD and 27 with UC) with various levels of disease activity.

The total IgG levels in patients with UC were significantly increased, for both active and inactive disease, compared to those of patients with CD. The IgG1 concentration in patients with UC (7+/-0.77 mg/ml) was significantly higher than in patients with CD (5.6+/-0.61 mg/ml) (p<0.02). The IgG2 levels in CD were significantly higher than those of UC (4.6+/-0.64 vs. 3.8+/-0.57 mg/ml) (p<0.05). The IgG4 levels of UC patients were significantly higher than those of the CD patients (0.39+/-0.06 vs. 0.29+/-0.05 mg/ml) (p<0.05). No significant differences were found in the serum concentrations of IgG3, IgA and IgM between the two groups. There was a negative correlation between the various indices of disease activity and the concentration of IgG3 in patients with UC (p<0.01), and a positive correlation in patients with CD for IgG1 (p<0.001), IgG2 (p<0.001) and IgA (p<0.01).

In IBD some of the IgG immunoglobulin subclass concentration changes correlate, positively or negatively, with disease activity and therefore could be used as additional markers of it. However, serum immunoglobulin levels cannot be used to differentiate between UC and CD.