deficiency and its impact on plasma cells and immunoglobulin expression in murine small intestinal mucosa.

The alternative (noncanonical) nuclear factor-κB (NF-κB) signaling pathway predominantly regulates the function of the p52/RelB heterodimer. Germline 2 deficiency in mice leads to loss of p100/p52 protein and offers protection against a variety of gastrointestinal conditions, including azoxymethane/dextran sulfate sodium (DSS)-induced colitis-associated cancer and lipopolysaccharide (LPS)-induced small intestinal epithelial apoptosis. However, the common underlying protective mechanisms have not yet been fully elucidated. We applied high-throughput RNA-Seq and proteomic analyses to characterize the transcriptional and protein signatures of the small intestinal mucosa of naïve adult mice. Those data were validated by immunohistochemistry and quantitative ELISA using both small intestinal tissue lysates and serum. We identified a B-lymphocyte defect as a major transcriptional signature in the small intestinal mucosa and immunoglobulin A as the most downregulated protein by proteomic analysis in mice. Small intestinal immunoglobulins were dramatically dysregulated, with undetectable levels of immunoglobulin A and greatly increased amounts of immunoglobulin M being detected. The numbers of IgA-producing, cluster of differentiation (CD)138-positive plasma cells were also reduced in the lamina propria of the small intestinal villi of mice. This phenotype was even more striking in the small intestinal mucosa of mice, although these mice were equally sensitive to LPS-induced intestinal apoptosis as their wild-type counterparts. NF-κB2/p52 deficiency confers resistance to LPS-induced small intestinal apoptosis and also appears to regulate the plasma cell population and immunoglobulin levels within the gut. Novel transcriptomic analysis of murine proximal intestinal mucosa revealed an unexpected B cell signature in mice. In-depth analysis revealed a defect in the CD38+ B cell population and a gut-specific dysregulation of immunoglobulin levels.