Granulocyte-Macrophage Colony Stimulating Factor Auto-Antibodies Are Produced by Lamina Propria Mononuclear Cells Isolated From Ileal Strictures of Pediatric Patients With Crohn Disease Undergoing Ileo-Cecal Resection

Abstract

G A A b st ra ct s that the STAT3 risk allele would be associated with increased cellular responsiveness to IL6 stimulation as measured by STAT3 tyrosine phosphorylation. Methods: B cells were isolated by magnetic bead columns from peripheral blood samples obtained from 69 pediatric IBD patients and transfected with EBV to create immortalized EBV-transformed lymphoblastoid cell lines (EBLs). Patients were genotyped for the STAT3 rs744166 and JAK2 rs10758669 risk alleles. EBLs selected for experimentation included STAT3 AA or GG (A=risk) while including only those which were also JAK2 AA (homozygote for the non-risk allele). EBLs were cultured overnight in serum-free media with 1x106 cells/mL and then stimulated with 100 ng/mL IL-6 for 30 minutes prior to analysis. Analyses included flow cytometry for cell surface IL-6 receptor and Glycoprotein130 (GP130) and intracellular pSTAT3 and pSTAT1; Real Time Polymerase Chain Reaction (RT-PCR) for STAT3, JAK2, and GP130; and western blot for nuclear pSTAT3 and pSTAT1, cytosolic STAT3, STAT1, JAK2, GP130, and IL6 receptor, and membrane fraction JAK2. Protein bands were quantified by normalized chemoluminescent arbitrary units (AU) via LAS Image Reader and MultiGauge Software (Fujifilm®). Differences were tested using unpaired and paired t-tests in GraphPad Prism Software®. Results: Pediatric IBD patient demographics did not vary by STAT3 genotype (age 15.6 vs 14.3 years, percent male 50 vs 40, CD patients 2 vs 2, UC patients 8 vs 6). Neither cell surface IL-6 receptor or GP130; cytosolic abundance of STAT3, STAT1, JAK2, GP130, IL-6 receptor; nor messenger RNA expression of STAT3, JAK2, or GP130 varied by STAT3 genotype. The mean nuclear protein pSTAT3 AU following IL-6 stimulation was 31.5 AU in EBLs from patients homozygous for the STAT3 risk allele compared to 19.1 AU in those lacking the STAT3 risk allele (p=0.04). The mean nuclear protein pSTAT1 AU following IL-6 stimulation was inversely 2.8 AU in EBLs from patients homozygous for the STAT3 risk allele compared to 4.3 AU in those lacking the STAT3 risk allele (p=0.001). The mean membrane fraction JAK2 AU was 80.2 AU in EBLs from patients homozygous for the STAT3 risk allele compared to 24.9 AU in those lacking the STAT3 risk allele (p= 0.008). Conclusions: The STAT3 genetic variant which increases risk for IBD is associated with increased JAK2 membrane fraction abundance and increased IL-6 dependent STAT3 tyrosine phosophorylation in EBV-transformed lymphocytes. These differences in cell signaling may promote IBD risk via STAT3 dependent effects upon T-lymphocyte differentiation and survival.