Nfkb2 deficiency and its impact on the murine small intestinal mucosa

The alternative (non-canonical) nuclear factor-kappa B (NF-?B) signalling pathway predominantly regulates the function of the p52/RelB heterodimer. Germline Nfkb2 deficiency in mice leads to loss of p100/p52 protein and offers protection against a variety of gastrointestinal conditions, such as azoxymethane/dextran sulfate sodium (DSS)-induced colitis-associated cancer and lipopolysaccharide (LPS)-induced small intestinal epithelial apoptosis. However, the common underlying protective mechanisms are not yet fully understood. Here we applied RNA sequencing and identified a B-lymphocyte defect as the major signature in the small intestinal mucosa of naïve adult Nfkb2-/- mice. Proteomics analysis also revealed a dramatic decrease in small intestinal immunoglobulin A levels, and this was validated by quantitative ELISA in both small intestinal lysates and serum. Moreover, the numbers of IgA-producing, CD138+ve plasma cells were also reduced in the lamina propria of the small intestinal villi of Nfkb2-/- mice. This phenotype was even more striking in the small intestinal mucosa of RelB-/- mice, although these mice were equally sensitive to LPS-induced intestinal apoptosis as their RelB+/+ wild-type counterparts. Therefore, p52 deficiency offers resistance to LPS-induced intestinal apoptosis and appears to regulate the plasma cell population within the gut.