Maarten Cozijnsen

77 Chapter 4 Infliximab impacts leukocyte RNA expression and serum inflammatory proteins Infliximab treatment homogeneously reduces the expression and concentration of Th1 related genes and proteins RNA expression analysis revealed significant downregulation of the IFN-γ and Th1 related genes IFNGR1 , JAK2 , STAT1 and IRF1 in peripheral blood leukocytes of patients treated with infliximab (Figure 2A). In addition, protein analysis demonstrated reduced concentrations of the Th1 related proteins CXCL9, CXCL10 and CXCL11, PD-L1, IFN-gamma, IL-12B, IL-18 and IL-18R1 in sera of infliximab treated patients (Figure 2B). We tested the association between RNA expression / protein concentration and SESCD scores (n=18) in a pooled analyses of baseline samples and samples at week 10 from patients treated with either infliximab or prednisolone (Table 2). JAK2 and IRF1 RNA expression in blood leukocytes were positively associated with SESCD, as were serum concentrations of CXCL9, CXCL10, CXCL11, PD-L1, IFN-gamma, IL-18 and IL-18R1. RNA expression of IFNGR1 and STAT1 in blood leukocytes and serum concentration of IL-12B were not significantly associated with SESCD, although STAT1 and IL-12B were almost significant (p-value between 0.05 and 0.01). Infliximab treatment reduces expression of s100 calcium binding proteins and concentration of several neutrophil chemo attractants RNA expression analysis revealed downregulation of mRNA S100A6 , S100A8 , S100A9 and S100A12 in blood leukocytes of infliximab treated patients (Figure 3A). EN-RAGE (S100A12) concentrations – the only S100 protein present in the proteomics Inflammation panel – were also reduced in sera of infliximab treated patients (Figure 3B). Furthermore, concentrations of the heterodimer of S100A8 and S100A9, a complex also known as calprotectin, were reduced in the feces of patients treated with infliximab (Figure 1A; p<0.001). S100 proteins are predominantly expressed by neutrophils, which were also decreased in concentration in these patients. Secondly, we found reduced serum concentrations of CXCL1, CXCL5 and CXCL8. These chemokines are known to recruit CXCR1/2+ neutrophils to sites of inflammation. CSF2 gene expression was not significantly downregulated in blood leukocytes and was not part of the proteomics Inflammation panel. All RNA expression of S100 calcium binding proteins in blood leukocytes positively associated with SESCD in the pooled analyses of baseline samples and samples at week 10 (Table 3). Concentrations of CXCL1, CXCL5, CXCL8 and EN-RAGE (S100A12) in serum were not significantly associated with SESCD; although CXCL1 was almost significant (p-value between 0.05 and 0.01).