Immunopathogenesis of Granulomas in Chronic Inflammatory Diseases : Relevance to diagnostics, biomarkers and treatment

Granulomas are formed in chronic immune mediated diseases such as sarcoidosis and Crohn’s disease as a sign of chronic inflammation. These diseases present with different clinical features, yet overlap in treatment and possibly immunopathogenesis. In this thesis we studied the involvement of B cells in Crohn’s disease in peripheral blood and inflamed intestinal tissue. As B cells showed to be numerously present in granulomatous tissue we analyzed whether additional B-cell staining would lead to an increase in granuloma detection in patients with Crohn’s disease. The effect of infliximab on B-and T-cell subsets was studied in patients with sarcoidosis before and during therapy in order to find immunological markers predicting therapeutic success. Furthermore, the effect of infliximab in patients with neurosarcoidosis was described in a multicenter cohort. With this thesis, we provide new evidence for the involvement of B cells in the immunopathogenesis of granulomatous inflammatory diseases. This opens new targeted treatment options for these disorders, by either targeting B cells or through B-T cell interactions

B-cell dysregulation in Crohn's disease is partially restored with infliximab therapy

Background: B-cell depletion can improve a variety of chronic inflammatory diseases, but does not appear beneficial for patients with Crohn's disease. Objective: To elucidate the involvement of B cells in Crohn's disease, we here performed an 'in depth' analysis of intestinal and blood B-cells in this chronic inflammatory disease. Methods: Patients with Crohn's disease were recruited to study B-cell infiltrates in intestinal biopsies (n = 5), serum immunoglobulin levels and the phenotype and molecular characteristics of blood B-cell subsets (n = 21). The effects of infliximab treatment were studied in 9 patients. Results: Granulomatous tissue showed infiltrates of B lymphocytes rather than Ig-secreting plasma cells. Circulating transitional B cells and CD21low B cells were elevated. IgM memory B cells were reduced and natural effector cells showed decreased replication histories and somatic hypermutation (SHM) levels. In contrast, IgG and IgA memory B cells were normally present and their Ig gene transcripts carried increased SHM levels. The numbers of transitional and natural effector cells were normal in patients who responded clinically well to infliximab. Conclusions: B cells in patients with Crohn's disease showed signs of chronic stimulation with localization to granulomatous tissue and increased molecular maturation of IgA and IgG. Therapy with TNFα-blockers restored the defect in IgM memory B-cell generation and normalized transitional B-cell levels, making these subsets candidate markers for treatment monitoring. Together, these results suggest a chronic, aberrant B-cell response in patients with Crohn's disease, which could be targeted with new therapeutics that specifically regulate B-cell function

Infliximab treatment in pathology-confirmed neurosarcoidosis

OBJECTIVE: To assess the efficacy and risks of treatment with infliximab (anti-tumor necrosis factor alpha) in pathology-confirmed neurosarcoidosis. METHODS: In a retrospective study in 2 tertiary referral centers in the Netherlands, we analyzed clinical characteristics, complications, and outcome of patients with neurosarcoidosis treated with infliximab. RESULTS: Twenty-eight patients were identified with a mean age of 42 years. Neurosarcoidosis presented with a cerebral parenchymal localization in 16 (59%), pituitary gland/hypothalamic sarcoidosis in 15 (54%), peripheral nerve involvement in 12 (43%), and chronic meningitis in 11 patients (41%). Initial treatment response after the start of infliximab was complete remission in 6 (21%) and improvement in 14 (50%), whereas 7 patients had stable disease (25%), and 1 (4%) deteriorated and died. At the end of follow-up, with a median of 32 months, 5 patients (18%) had died, and 2 (40%) were using infliximab at the time of death. Tapering or discontinuation of corticosteroids without a relapse was achieved in 19 of 28 patients (68%). In patients with decreasing dosing or discontinuation of infliximab, a relapse occurred in 5 of 19 patients (26%). Complications of infliximab were reported in 10 of 28 patients (36%) and mainly consisted of infections in 8 (29%). CONCLUSION: Infliximab is an effective treatment in neurosarcoidosis leading to remission or improvement in 70%. The mortality rate in infliximab-treated patients was substantial, indicating the severity of disease and treatment-associated complications. CLASSIFICATION OF EVIDENCE: This study provides Class IV evidence that in people with pathology-confirmed neurosarcoidosis, infliximab is beneficial