The involvement of IgH enhancer HS1.2 in the pathogenesis of Crohn's disease: how the immune system can influence a multifactorial disease.

OBJECTIVE: To study the 3' immunoglobulin heavy-chain regulatory region (3' RR) enhancer complex, active in class switching recombination and in B-cells, in Crohn's disease. PATIENTS AND METHODS: A total of 167 patients [79 females (47.3%) and 88 males (52.7%)] affected by Crohn's disease were enrolled in the study. As a control, we included 64 healthy subjects, age and sex matched, from the same geographical area. Blood tests were performed on all subjects to determine their antibody levels and to detect the presence of any possible infections. We conducted a selective PCR, which amplified the hs1.2-A region. The nested second PCR to amplify the polymorphic core of the enhancer was performed. RESULTS: No differences between cases and controls were observed with respect to sex distribution (43.8% females among controls and 49.5% among cases), age, tTG IgA, RF, serum or secretory IgA, IgG1, IgG2 and IgG3. No correlation was found between both seric and secretory immunoglobulins levels, with except of statistically significant differences between cases and controls with respect to IgA and IgG ASCA positivity (p<0.001), serum IgG4 (p<0.001) and IgD (p=0.001). CONCLUSIONS: We have demonstrated that in Crohn's disease, the HS1,2 immunoglobulins enhancer is not implicated in the disease pathogenesis. Moreover, we have found that IgG4 levels are lower in Crohn's disease patients than in controls; these data may be related to an impairment of number and function of Tregs, further linked to the presence of tissue inflammation. Crohn's disease is a complex multifactorial disease. The pathogenesis of Crohn's disease is incompletely understood although it is clear that the disease involves multiple interacting agents.