The discriminative capacity of soluble Toll-like receptor (sTLR)2 and sTLR4 in inflammatory diseases

ten Oever, Jaap; Kox, Matthijs; van de Veerdonk, Frank L; Mothapo, Khutso M; Slavcovici, Adriana; Jansen, Tim L; Tweehuysen, Lieke; Giamarellos-Bourboulis, Evangelos J; Schneeberger, Peter M; Wever, Peter C; Stoffels, Monique; Simon, Anna; van der Meer, Jos WM; Johnson, Melissa D; Kullberg, Bart-Jan; Pickkers, Peter; Pachot, Alexandre; Joosten, Leo AB; Netea, Mihai G

sTLR2 and sTLR4 release during human endotoxemia sTLR2 and sTLR4 plasma concentrations displayed a distinct pattern after LPS infusion ( Figure 2 ). Before LPS administration, sTLR2 and sTLR4 levels were undetectable or low in all volunteers. sTLR4, TNFα, IL-6 and IL-10 concentrations increased after LPS infusion and reached a peak concentration at 2 hours LPS infusion; sTLR2 and IL-1Ra peaked after 4 hours. The mean peak values (± SEM) were 357 ± 94 ng/ml for sTLR2, 10.5 ± 2.3 ng/ml for sTLR4, 836 ± 288 pg/ml for TNFα, 926 ± 145 pg/ml for IL-6, 90 ± 17 pg/ml for IL-10, and 26081 ± 2213 pg/ml for IL-1Ra, respectively. The AUC of sTLR4 showed no correlation with the AUCs of sTLR2 (r s 0.03, P = 0.94), IL-6 (r s -0.07, P = 0.83), TNFα (r s -0.07, P = 0.80), IL-10 (r s 0.22, P = 0.52), and IL-1Ra (r s 0.14, P = 0.69). However, sTLR2 showed a strong positive correlation with TNFα (r s 0.80, P = 0.003), IL-6 (r s 0.65, P = 0.03). sTLR2 showed a trend towards a positive correlation with IL-1Ra (r s 0.57, P = 0.06), and a negative with IL-10 (r s -0.58, P = 0.06), respectively. Cell-surface expression of TLR2 and TLR4 on monocytes varied extensively among the subjects without a clear pattern and did not correlate with sTLR2 and sTLR4 plasma levels ( Figure 2 ). Figure 3 shows the circulating concentrations of CRP, sTLR2 and sTLR4 in various infectious and non-infections inflammatory diseases. 394 patients and 29 healthy volunteers were included. For determination of CRP, samples of 351 patients and 11 healthy volunteers were analyzed. CRP, sTLR2 and sTLR4 circulating concentrations were significantly higher in patients with infection compared with patients with non-infectious inflammation (Figure 4 , groups A and B). After correction for age and sex, the presence of an infection was still positively associated with CRP, sTLR2 and sTLR4: unstandardized coefficients 85 (95% CI 64-106, P < 0.001), 23 (95% CI 12-34, P < 0.001), and 6.2 (95% CI 4.2-8.2, P < 0.001), respectively. Age, but not sex, was also positively associated with the three biomarker concentrations. Furthermore, compared with patients suffering from viral infections, patients with bacterial infections displayed higher concentrations of CRP and sTLR4, but not sTLR2 (Figure 4 , groups C and D). Multivariate analysis with correction for age and sex showed all three biomarkers to be independently associated with the presence of a bacterial infection. Unstandardized coefficients for CRP, sTLR2 and sTLR4 were 113 (95% CI 79-147, P < 0.001), 19 (95% CI 0.2-39, P = 0.04) and 6.2 (95% CI 2.2-9.0, P = 0.01), respectively. Neither sex, nor age proved to influence the concentrations of CRP, sLTR2 and sTLR4.