86 EFFECTS OF PROPHYLACTIC ANTIBIOTICS ON TOLL-LIKE RECEPTOR (TLR) 2 AND 4 EXPRESSION ON PERIPHERAL BLOOD MONONUCLEAR CELLS (PBMC) IN PATIENTS WITH DECOMPENSATED CIRRHOSIS

Abstract

Background and Aims: TLRs are pivotal in the innate immune recognition of microbial structures, resulting in the production of proinflammatory cytokines, and the priming of an adaptive immune response. TLR4 recognises lipopolysaccharide on gram-negative (G−) bacteria, while TLR2 recognises peptidoglycan on gram-positives (G+). We aimed to determine whether TLR expression is altered in cirrhosis and if this is affected by treatment with antibiotics used to prevent spontaneous bacterial peritonitis (SBP). Methods: 62 patients were included (23 age/sex matched healthy controls and 39 Child-Pugh C cirrhotics). 29 cirrhotics were taking either norfloxacin or trimethoprim-sulfamethoxazole as prophylaxis against SBP and 10 were not receiving prophylaxis. Paired blood samples were taken from a further 7 patients before and after commencing prophylactic antibiotics. 40mls of blood was taken from each patient. PBMC were extracted using Ficoll-Paque density gradient centrifugation. PBMC expression of TLR2 and 4 was determined using flow cytometry, producing a ratio of the geometric mean of fluorescence intensity to that of a matched isotype control. Results are presented as medians relative to controls (control median = 1.0). Results: There were no differences in Child-Pugh score, age, disease aetiology or sex distribution between patients receiving antibiotics and those who were not. However, cirrhotic patients not taking antibiotics had significantly decreased TLR4 expression compared with both controls (0.74 vs. 1.0, p = 0.01) and patients receiving antibiotics (0.74 vs. 1.125, p = 0.01). There was no difference in TLR4 expression between antibiotic treated patients and controls (p = 0.88). Conversely, antibiotic treated patients expressed lower TLR2 compared to those not on antibiotics (0.909 vs. 1.091, p = 0.04). In the 7 patients with paired samples, TLR4 expression increased significantly from 0.689 to 1.331 (p = 0.002) following commencement of antibiotics, whilst there was a trend towards decreased TLR2 expression from 0.957 to 0.859 (p = 0.28). Conclusions: TLR4 expression is decreased in Child-Pugh C cirrhotics, but is restored by antibiotics targeting enteric G− bacteria. This suggests that the high incidence of G− sepsis in cirrhotics is in part due to downregulation of the host’s TLR4 dependant innate immune response and that this may be mediated by chronic exposure to G− bacterial products.