Intestinal immune regulatory signals govern gut homeostasis and is tightly controlled by the interaction of gut microbial gene products with pattern recognition receptors. The breakdown of such regulatory mechanisms may result in inflammatory bowel disease (IBD). Lactobacillus acidophilus contains unique surface layer proteins (Slps), including SlpA, SlpB, SlpX and lipoteichoic acid (LTA), which interact with pattern recognition receptors to mobilize immune responses. To demonstrate the role of SlpA in protective immune regulation, a strain of Lactobacillus acidophilus which solely expressed SlpA was generated. They demonstrated that its purified SlpA bind to the C-type lectin SIGNR3 to exert regulatory signals that result in mitigation of colitis, maintenance of healthy gastrointestinal microbiota, and protected gut mucosal barrier function. Interestingly, such protection was not observed in Slgnr3-/- mice, suggesting that the SlpA/SIGNR3 interaction plays a key regulatory role in colitis.
Lightfoot YL, et al. SIGNR3-dependent immune regulation by Lactobacillus acidophilus surface layer protein A in colitis. The EMBO Journal (2015) 34, 881-895