Patients and fecal microbiota analysis
Three AIP patients that met the diagnostic criteria for type 1 AIP [21] were enrolled in this study. They were treated with PSL for the induction of remission. Oral administration of PSL at an initial dose of 0.6–0.7 mg/kg followed by scheduled tapering regimen (5 mg every two weeks) successfully induced clinical remission in all patients, as evaluated by the disappearance of diffuse pancreatic swelling and reduction in serum IgG4 concentrations. The study protocol conformed to the ethical guidelines for human clinical research established by the Japanese Ministry of Health, Labor, and Welfare and was approved by the ethics committee at the Kindai University Faculty of Medicine. Written informed consent was obtained from all patients during enrollment.
Fecal samples were obtained from all three patients before, as well as two months after, the PSL treatment. Fecal microbiota analysis was performed as described previously [20, 22]. DNA samples extracted from the stool were subjected to polymerase chain reaction for the amplification of 16S ribosomal RNA (16S rRNA) V3 and V4 regions, followed by sequencing using the MIseq system (Illumina Japan, Tokyo, Japan). Sequence data were processed by Trimmomatic, Cutadapt, and Fastq-join programs; subsequently, operational taxonomic units (OTUs) were determined by using QIIME programs.