Beta-2-Microglobulin Regulates Sheep Susceptibility to Escherichia coliF17b in Intestinal Epithelial Cells

<i>Beta-2-microglobulin</i> (B2M) is a key component protein in the processing and presentation of major histocompatibility complex (MHC)-I antigens and plays an important role in the immune system regulation. Previous studies have shown that B2M is significantly overexpressed in the intestinal tissues of sheep that are resistant to <i>E. coli F17b</i> infection (defined by milder clinical symptoms post-challenge) compared to those that are susceptible (exhibiting severe diarrhea). Based on this finding, this study aimed to investigate whether B2M influences the adhesion of <i>E. coli F17b</i> to sheep intestinal epithelial cells (IECs) and to assess its role in regulating IEC proliferation and migration. We tested this by overexpressing and knocking down B2M in IECs, and then measured bacterial adhesion through colony counts and fimbrial gene expression (RT-qPCR). Moreover, cell health was assessed using proliferation (CCK-8 and EdU) and migration (scratch) assays. The results showed that upregulation of B2M expression inhibited <i>E. coli F17b</i> adhesion and promoted IEC proliferation and migration. Silencing B2M increased bacterial adhesion and impaired cell function. In summary, B2M helps protect sheep IECs from <i>E. coli F17b</i> by strengthening the epithelial barrier through improved cell growth, proliferation, and migration. These findings elucidate part of the host defense mechanism against <i>E. coli F17b</i>, providing a basis for further research.