Up-regμlation Of IgA Production In The Intestine By A Lactobacillus Rhamnosus GG-derived Protein

Objective Ig A is the abundant immunoglobulin in gut system and plays an important role in maintaining intestinal homeiastasis. Ig A induction take place through both T-cell-dependent and T-cell-independent pathways. Lactobacillus rhamnosus GG(LGG) is a naturally occurring gram-positive bacterium originally isolated from the healthy human intestine. P40, a LGG-derived protein, transactivates EGF receptor(EGFR) in intestinal epithelial cells, leading to amelioration of intestinal injury and inflammation. Since the intestinal microbiota contributes to Ig A production, this study aimed to determine the effects and mechanisms by which p40 regulates APRIL production in intestinal epithelial cells, leading to Ig A production in B cells.Methods 1. p40 was used to treat mouse small intestine epithelial(MSIE) cells.B cells isolated from mouse spleen were treated with p40 and p40-conditioned medium from MSIE cells with an APRIL neutralizing antibody.2. p40 was used to treat mouse small intestine epithelial(MSIE) cells with EGFR knock-down and inhibition of EGFR kinase activity and small intestinal enteroids from Egfrfl/fl-Vil-Cre mice with EGFR specifically deleted in intestinal epithelial cells and their littermate control, Egfrfl/fl mice.3. Egfrfl/fl-Vil-Cre and Egfrfl/fl mice were gavaged with p40-containing pectin/zein beads. April gene expression and protein levels in intestinal epithelial cells, B cell Ig A class switching, and IgA production were examined.Results 1. p40-conditioned media from MSIE cells increased B cell class switching to Ig A+ cells and Ig A production, which was suppressed by the APRIL neutrolizing antibody. Treatment of B cells with p40 did not show any effect on Ig A production.p40 stimulated gene expression and protein production of APRIL in MSIE cells.2. p40 stimulated gene expression and protein production of APRIL in MSIE cells, which were inhibited by blocking EGFR expression and kinase activity. April gene expression was up-regulated by p40 in enteroids from Egfrfl/fl, but not Egfrfl/fl-Vil-Cre mice.3. p40 treatment increased fecal Ig A levels, IgA+ plasma cells in lamina propria, and APRIL gene expression and protein production in small intestinal epithelial cells in Egfrfl/fl, but not Egfrfl/fl-Vil-Cre mice.Conclusion 1. p40 stimulates APRIL production in intestinal epithelial cells in vitro, which mediates increased Ig A production in B cells in the intestine.2. p40 stimulates APRIL production intestinal epithelial cells via EGFR/NF-?B pathways.3. p40 upregulates APRIL gene expression and protein production in small intestinal via EGFR pathways in vivo, resulting in the increased production of Ig A in gut.