Evaluation of Antibody Response to Polysaccharide Vaccine and Switched Memory B Cells in Pediatric Patients with Inflammatory Bowel Disease

BACKGROUND/AIMS: Inflammatory bowel disease (IBD) is a chronic disease of the gastrointestinal tract, whose etiologies are still unknown. This study was performed to evaluate the humoral immune response in terms of B cell functions in selected IBD patients. METHODS: Eighteen pediatric patients with IBD, including 12 cases of ulcerative colitis (UC) and six with Crohn disease (CD), were enrolled in this study. The pneumococcal vaccine was injected in all patients, and the IgG antibody level to the polysaccharide antigen was measured before and 4 weeks after injection. The B cell switch-recombination process was evaluated. RESULTS: Five patients with IBD (three CD and two UC) had defects in B cell switching, which was significantly higher than in controls (p=0.05). Ten patients had a specific antibody deficiency and exhibited a higher frequency of bacterial infection than the healthy group. The mean increased level of IgG after vaccination was lower in IBD patients (82.9+/-32.5 microg/mL vs 219.8+/-59.0 microg/mL; p=0.001). Among the patients who had an insufficient response, no significant difference in the number of switched memory B-cell was observed. CONCLUSIONS: A defect in B lymphocyte switching was observed in pediatric IBD patients, and especially in those patients with CD. Owing to an increased risk of bacterial infections in those patients with antibody production defects, pneumococcal vaccination could be recommended. However, not all patients can benefit from the vaccination, and several may require other prophylactic methods.

Expression of activation-induced cytidine deaminase gene in B lymphocytes of patients with common variable immunodeficiency

Common variable immunodeficiency [CVID] is a heterogeneous disorder characterized by reduced serum level of IgG, IgA or IgM and recurrent bacterial infections. Class switch recombination [CSR] as a critical process in immunoglobulin production is defective in a group of CVID patients. Activation-induced cytidine deaminase [AID] protein is an important molecule involving CSR process. The aim of this study was to investigate the AID gene mRNA production in a group of CVID patients indicating possible role of this molecule in this disorder. Peripheral blood mononuclear cells [PBMC] of 29 CVID patients and 21 healthy controls were isolated and stimulated by CD40L and IL-4 to induce AID gene expression. After 5 days AID gene mRNA production was investigated by real time polymerase chain reaction. AID gene was expressed in all of the studied patients. However the mean density of extracted AID mRNA showed higher level in CVID patients [230.95 +/- 103.04 ng/ml] rather than controls [210.00 +/- 44.72 ng/ml; P=0.5]. CVID cases with lower level of AID had decreased total level of IgE [P=0.04] and stimulated IgE production [P=0.02]; while cases with increased level of AID presented higher level of IgA [P=0.04] and numbers of B cells [P=0.02] and autoimmune disease [P=0.02]. Different levels of AID gene expression may have important roles in dysregulation of immune system and final clinical presentation in CVID patients. Therefore investigating the expression of AID gene can help in classifying CVID patients