Effects of antibiotics on expression and function of Toll-like receptors 2 and 4 on mononuclear cells in patients with advanced cirrhosis

Background & Aims

Toll-like receptors (TLRs) are critical to innate immune responses. TLR4 recognises Gram-negative bacteria, whilst TLR2 recognises Gram-positive. We examined TLR expression and function in cirrhosis, and whether this is affected by antibiotic therapy.

Methods

Sixty-four subjects were included (23 controls and 41 Child-Pugh C cirrhotic patients). Thirty patients were taking norfloxacin or trimethoprim-sulfamethoxazole as prophylaxis against bacterial peritonitis and 11 were not. In a second study, 8 patients were examined before and after commencement of antibiotics. Monocyte expression of TLR2 and 4 was determined by flow cytometry. Monocytes from the patients with paired samples were stimulated using TLR ligands and TNF-α production measured.

Results

Patients not taking antibiotics had significantly decreased TLR4 expression compared with controls (0.74 vs. 1.0, p=0.009) and patients receiving antibiotics (0.74 vs. 0.98, p=0.02). There were no differences with regard to TLR2. In the patients with paired samples, TLR4 expression increased (0.74–1.49, p=0.002) following antibiotic use, whilst again, there was no change in TLR2 expression (0.99 vs. 0.92, p=0.20). TLR4-dependent TNF-α production increased following antibiotic use (1077 vs. 3620pg/mL, p<0.05), whilst TLR2-dependent production was unchanged.

Conclusions

TLR4 expression is decreased in patients with Child-Pugh C cirrhosis, but is restored by antibiotics targeting enteric Gram-negative bacteria. TLR4-dependent cytokine production also increases significantly following antibiotic therapy. This suggests that the high incidence of Gram-negative infection in cirrhotic patients is in part due to down-regulation of the TLR4-dependant immune response and that the efficacy of antibiotic prophylaxis is contributed to by modulation of innate immunity.

Abbreviations: TLR, Toll-like receptor, LPS, lipopolysaccharide, SBP, spontaneous bacterial peritonitis, PBMC, peripheral blood mononuclear cell, P3C, Pam-3-Cys, ELISA, enzyme-linked immunosorbent assay, TNF, tumour necrosis factor, PBS, phosphate-buffered saline, FCS, foetal calf serum, DMSO, dimethyl sulfoxide

Keywords: Toll-like receptors, Innate immunity, Endotoxin, Cirrhosis, Spontaneous bacterial peritonitis, Antibiotics, Cytokine