Impact of human sepsis on CCCTC-binding factor associated monocyte transcriptional response of Major Histocompatibility Complex II components

Abstract

BackgroundAntigen presentation on monocyte surface to T-cells by Major Histocompatibility Complex, Class II (MHC-II) molecules is fundamental for pathogen recognition and efficient host response. Accordingly, loss of Major Histocompatibility Complex, Class II, DR (HLA-DR) surface expression indicates impaired monocyte functionality in patients suffering from sepsis-induced immunosuppression. Besides the impact of Class II Major Histocompatibility Complex Transactivator (CIITA) on MHC-II gene expression, X box-like (XL) sequences have been proposed as further regulatory elements. These elements are bound by the DNA-binding protein CCCTC-Binding Factor (CTCF), a superordinate modulator of gene transcription. Here, we hypothesized a differential interaction of CTCF with the MHC-II locus contributing to an altered monocyte response in immunocompromised septic patients.MethodsWe collected blood from six patients diagnosed with sepsis and six healthy controls. Flow cytometric analysis was used to identify sepsis-induced immune suppression, while inflammatory cytokine levels in blood were determined via ELISA. Isolation of CD14++ CD16—monocytes was followed by (i) RNA extraction for gene expression analysis and (ii) chromatin immunoprecipitation to assess the distribution of CTCF and chromatin modifications in selected MHC-II regions.ResultsCompared to healthy controls, CD14++ CD16—monocytes from septic patients with immune suppression displayed an increased binding of CTCF within the MHC-II locus combined with decreased transcription of CIITA gene. In detail, enhanced CTCF enrichment was detected on the intergenic sequence XL9 separating two subregions coding for MHC-II genes. Depending on the relative localisation to XL9, gene expression of both regions was differentially affected in patients with sepsis.ConclusionOur experiments demonstrate for the first time that differential CTCF binding at XL9 is accompanied by uncoupled MHC-II expression as well as transcriptional and epigenetic alterations of the MHC-II regulator CIITA in septic patients. Overall, our findings indicate a sepsis-induced enhancer blockade mediated by variation of CTCF at the intergenic sequence XL9 in altered monocytes during immunosuppression.

Postoperative abdominal sepsis induces selective and persistent changes in CTCF binding within the MHC-II region of human monocytes

“…Recently, we could demonstrate in circulating monocytes of patients with sepsis, that an increased CTCF-occupancy at this intergenic region is associated with selective changes in adjacent HLA-gene expression. These findings indicate a CTCF mediated enhancer blockade as a potential mechanism contributing to an immunocompromised phenotype [18].…”

“…The impact of CTCF on global gene expression has been investigated in numerous cell types including those of the innate immune system [23]; however, its role in the transcriptional regulation of antigen presentation during postoperative human sepsis has not been elucidated so far. Based on previous work hinting towards a CTCF-mediated enhancer blockade of selected HLA genes during critical illness [18], we analysed global CTCF occupancy within the MHC-II in patients suffering from postoperative abdominal sepsis. Compared to a matched control cohort, we could demonstrate that postoperative sepsis was associated with a selective and persistent increase in CTCF enrichment at binding sites located next to classical HLA genes that code for proteins expressed on the surface of antigen-presenting cells.…”

“…Cell culture experiments by Majumder and colleagues revealed that the enhanceosome complex interacts with CTCF within the MHC-II region in an intergenic region separating the genes HLA-DRB1 and HLA-DQA1, which seems to be responsible for changes in HLA class II gene regulation [16,17]. We could recently show that increased CTCF-occupancy at this intergenic region is associated with differential expression of spatially related genes in critically ill and immunocompromised patients [18]. To elucidate the overall CTCF occupancy within the MHC-II region and its potential impact on HLA gene expression during postoperative abdominal sepsis, we analyzed all known CTCF binding sites within MHC II as identified by Majumder and Boss [22].…”

“…Regulation of MHC-II has been shown to depend on the transcriptional co-activator CIITA and its interplay with distinct DNA-binding factors with subsequent formation of an enhanceosome complex [26]. In previous work, the CIITA promoter located on the short arm of chromosome 16 displayed a marked reduction of the histone marks H3K4me3 and H3K27ac in patients with sepsis compared to healthy control individuals [18,27]. Because these Cytokine levels in plasma and supernatants from ex-vivo stimulated samples.…”

Sepsis impedes EAE disease development and diminishes autoantigen-specific naive CD4 T cells

“…This reduction compounded with the already reduced number of myeloid cells leading to ~100 fold reduction in MHC II-expressing cells in CLP hosts ( Figure 1—figure supplement 3g,i ). Prior studies have demonstrated alterations in MHC expression by myeloid cells which are dysregulated following sepsis ( Jensen et al, 2020 ; Monneret et al, 2006 ; Siegler et al, 2018 ). MHC II expression is not only a marker of activation of these cell populations but also serves to present antigen to CD4 T cells, including autoreactive T cells that are critical mediators of disease in EAE.…”