Increased Toll-like receptor 9 expression by B cells from inflammatory bowel disease patients.

Background: Toll-like receptors (TLRs) are important mediators of the innate immune response. Our aim was to evaluate TLR9 expression in peripheral B cells, taken from inflammatory bowel disease (IBD) patients before and after anti-inflammatory treatment. Nineteen patients with IBD (12-crohn's disease, 7-ulcerative colitis) and 18 healthy controls were included in the study. Disease severity was assessed using the Pediatric/Adults crohn's disease activity index and the ulcerative colitis activity index as needed. Accordingly, patients were classified as mild, moderate or severe disease. Peripheral B cells isolated from IBD patients, before and after anti-inflammatory treatment, and from the control group, were cultured for 24 h with and without CpG oligodeoxynucleotides (ODN-CpG) 0.5 μM. TLR9 expression by memory B cells (CD19+CD27+) was assessed by flow cytometry.

Results: We found that TLR9 expression by peripheral B cells was significantly higher in IBD patients than that in healthy controls (12.42 ± 9.5 MFI vs. 6.0 ± 2.6 MFI p = 0.02). The addition of ODN-CpG to B cells resulted in a significantly increase of TLR9 expression in B cells from healthy controls (6.5 ± 3.2 MFI vs. 8.8 ± 4.2 MFI p = 0.007). On the contrary, B cells from IBD patients only partly respond to the addition of ODN-CpG after anti-inflammatory treatment (6.3 ± 3.8 vs. 7.3 ± 3.7, p = 0.1). TLR9 expression was positively correlated with IBD disease severity (r = 0.681, p < 0.0001).

Conclusions: TLR9 expression in memory B from IBD patients is elevated and associated with disease severity.