Pathogenesis of Crohn's disease (CD) is thought to involve the chronic activation of T helper 1 (Th1)- and Th17-mediated inflammation, such as the production of interferon-gamma (IFN-γ) and interleukin 17 (IL-17). However, studies have also shown that although IFN-γ is required, IFN-γ-producing or T-bet-expressing Th1 cells are dispensable. We therefore examined T-bet-expressing B cells as another source of IFN-γ that potentially supported intestinal inflammation in CD patients. We found that the frequencies of T-bet-expressing B cells were significantly upregulated and abundantly present in the gut of active, but not quiescent, CD patients. The frequencies of T-bet-expressing B cells were also directly correlated with CD disease activity. These T-bet B cells were almost exclusively IgG expressing and produced significantly higher amounts of IFN-γ, IL-6, and IL-12 than IgA- and IgM-expressing T-bet B cells. These B cells also supported IFN-γ production of CD4 T cells. T-bet expression was induced in vitro in peripheral blood B cells through the stimulation of B-cell receptor (BCR), Toll-like receptor 7 (TLR7), and IFN-γ, which resembled gut T-bet B cells in terms of elevated IFN-γ. We found that these stimulated B cells, but not unstimulated B cells, supported the IFN-γ and IL-12 production from autologous CD4 T cells. In addition, in patients with higher gut T-bet B-cell percentage, a higher frequency of gut-infiltrating IFN-γ and IL-12 T cells was also observed. Together, our results suggested that T-bet-expressing B cells could contribute to the intestinal Th1 inflammation in CD patients.

Abstract

Follicular helper T cells (Tfh) represent a distinct subset of CD4+ T cells specialized in providing help to B lymphocytes. Studies have indicated that Tfh in circulating blood can act as a prognostic marker for diseases. In the current study, we investigated the percentages of circulating Tfh (CTfh) in Crohn's disease (CD) and CD-associated colorectal cancer (CRC). CTfh and it subtypes were determined by measuring CD3, CD4, CXCR5, CXCR3, and CCR6 using flow cytometry in 32 healthy controls and 78 CD patients, which included 16 CD-associated CRC. Data showed that proportion of CTfh in CD4+ T cells was significantly increased in CD patients (9.8 %) than in controls (5.1 %) (p < 0.01). Further analysis revealed that the upregulation of CTfh was contributed by CTfh-Th1 subtype and CTfh-Th17 subtype. Investigating the behavior of the patients demonstrated that prevalence of CTfh was significantly elevated in penetrating CD (20.9 %) than inflammatory CD (8.2 %) or stricturing CD (7.5 %). In addition, we analyzed CTfh in CD-associated CRC, and identified that patients with CRC had 1.59-fold higher percentage of CTfh than patients without CRC (p < 0.01). Furthermore, the distribution of CTfh subsets was significantly altered in patients with the cancer. This study suggests the involvement of CTfh in CD and CD-associated CRC, in which the effect of CTfh is partially different between these two diseases.

No abstract