Anti–tumor necrosis factor (TNF) therapy has become a standard therapy for severe inflammatory bowel diseases (IBD), but its effect on B lymphocytes is largely unexplored. In this study we investigated peripheral blood B cells, B-cell subsets, and CD40 expression in patients with IBD before and during anti-TNF therapy with infliximab (IFX).Methods:
Blood was taken from healthy controls (n = 52) and patients with active IBD before (n = 46) and/or during anti-TNF therapy (n = 55). B-cell markers were detected by immunofluorescent staining and FACS analysis. Patients were classified as responders or nonresponders to anti-TNF therapy.Results:
We found a numerical deficiency of circulating CD19+ B cells, a lower activation state (CD40 expression) and lower proportions of CD5+ B cells and IgM+IgD+CD27+ preswitched memory cells among B cells in active patients with IBD before IFX therapy compared with healthy controls. IFX treatment increased CD19+ B-cell numbers as well as the proportions of named B-cell subsets in responders but not in nonresponders. IFX more effectively upregulated CD40 expression in responders than in nonresponders. Restoration of B cells correlated with the biological response to therapy (C-reactive protein). Trough serum levels of IFX correlated with the number of B cells during therapy.Conclusions:
A lower number of circulating B cells, a low CD40 expression, and a decrease in the proportion of CD5+ and in the preswitched memory subset characterize active IBD. Restoration of these abnormalities correlates with the clinical response to anti-TNF therapy. The mechanism for this effect on B cells should be further explored.