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Peptide HLA arrays were produced by BioCopy GmbH. For this, 5k-PDMS chips containing the peptide arrays were warmed up to RT. Peptide arrays were then cleaned with an N₂ gas stream to remove dust. Subsequently, 900 pl of HLA solution (200 $\mathrm{\mu }$ g/mL HLA, 1M betaine (Sigma Aldrich, Germany), 0.07% BSA (Carl Roth, Germany), 0.035% Tween 20 (Sigma Aldrich, Germany) 1xPBS, pH 7,4 (Sigma Aldrich, Germany)) was spotted into each well of the peptide arrays using a non-contact microarray printer (iTWO, M2-Automation). The final HLA to peptide ration was 1/11. Spotting was carried out at 80% humidity to prevent evaporation of the HLA solution during the process. Next, 3D-SA highSCORE slides were placed on the 5k-PDMS chips containing the peptide-HLA mix, resulting in chip-highSCORE slide sandwiches. To transfer the newly formed peptide-HLA complexes from the cavities of the 5k-PDMS chips onto the highSCORE slides, slides were pressed onto the chips with a force of 165 N using custom-made presses. To completely immobilize the peptide-HLA complexes on the 3D-SA surface of the highSCORE slides via the biotinylated HLA, the sandwiches were incubated overnight at 4  ${}^{\circ }$ C in the presses. highSCORE measurements of the peptide-HLA arrays were carried out on the following day.

After 7 days, treated and control animals were anesthetized and sacrificed by cervical dislocation; livers were immediately harvested under sterile conditions and homogenized using the Omni TH homogenizer with a 7-mm generator probe (Omni International, Kennesaw, GA, United States) in 5 ml sterile 1X PBS pH 7.4 (Sigma, St. Louis, MO, United States). One milliliter of the liver homogenate was spread onto the surface of MacConkey agar for enterobacteria (Difco Laboratories, Detroit, MI, United States). The plates were then aerobically incubated at 37°C for 48 h. Translocation was considered to have occurred when colonies were observed on the agar plates because the liver is an organ normally devoid of bacteria (Gregory et al., 1996 (link)).

The small intestine of treated and control animals was flushed with 5 ml of 1X PBS pH7.4 (Sigma, St. Louis, MO, United States) and this fluid was centrifuged at 10,000 g at 4°C for 10 min to separate particulate material. The supernatant was collected and kept frozen at −80°C until use. IL-6 and IL-10 were determined in supernatant using the corresponding mouse ELISA Set (BD OptEIA, BD Biosciences PharMingen, San Diego, CA, United States) with catalog numbers respectively: 555240 and 555252. For IL-6, capture antibody was diluted at 1:250 in coating buffer (BD OptEIA, BD Biosciences PharMingen, San Diego, CA, United States) while the detection antibody was diluted at 1:259 in assay diluent (BD OptEIA, BD Biosciences PharMingen, San Diego, CA, United States). For Il-10, dilutions were respectively 1:250 dilution in coating buffer for capture antibody while 1:250 dilution in assay diluent for the detection antibody. For secretory IgA, the level of IgA was analyzed by DAS-ELISA using affinity-purified goat anti-mouse IgA antibodies (α-chain specific) was added at 1.25 mg/well and horseradish-peroxidase conjugated anti-IgA specific antibodies at 1.25 mg/well (Sigma Chemical Co., St Louis, MO, United States). Absorbance was read at 450 nm within 30 minutes of stopping reaction with wave length correction 570 nm.