B1a lymphocytes in ulcerative colitis

Background and aims: B1a lymphocytes (CD5+) are the major contributors of natural antibodies (Ab) implicated in the initial protection against several infections. The aim of this study was to assess the expression of these cells in the peripheral blood of ulcerative colitis (UC) patients who underwent restorative proctocolectomy (RPC) and others who were not operated on. Materials and methods: The blood concentration ofCD5+ B cells was analysed by three-colour flow cytometry. Blood was collected from 38 UC patients, 20 of whom had undergone RPC and compared with the results in 18 healthy controls and in 12 familial adenomatous polyposis (FAP) patients who had undergone RPC. We were interested in evaluating if there was any correlation between B1a blood cell concentration and ESR and CRP levels, clinical, endoscopic and histological activity, perinuclear anti-neutrophil cytoplasmic antibody (pANCA) and extra-intestinal symptoms. Results: B1a cell blood concentration was reduced in non-operated UC patients (20.7 ± 4.6/μl) with respect to that in healthy controls (71.1 ± 18.0/μl, p <0.05). It was also lower in UC patients with RPC (24.9 ± 1.0/μl) compared to RPC for FAP (48.2 ± 6.2, p <0.05). B1a cell rate correlated inversely in UC patients with ESR (R = -0.41, p <0.05) and CRP levels (R = -0.47, p = 0.01). Conclusion: B1a cell concentration was reduced in the blood of patients with UC even after the diseased organ was surgically removed by proctocolectomy. As these cells play an important role in natural immunity against luminal stimuli, consistently lower levels that are found in UC patients could be responsible for the impaired immunologic response to gut antigens in this disease.