Masked microbes

Some pathogenic bacteria have a clever strategy for evading our innate immune system - make themselves look like our red blood cells. Our immune system has been programmed to not attack our own cells, for obvious reasons. These wily bacteria come decorated with our blood group antigens (the carbohydrates that govern our blood type). The illustration below shows their attempted masquerade. But the Cummings group has found that we may be one step ahead. In Stowell SR, et al. “Innate immune lectins kill bacteria expressing blood group antigen.”  Nature Med. 2010 16, 295-301, they show that we express two isoforms of the glycan-binding protein known as galectin to kill the bacteria by recognizing the blood group antigen. Presumably, by selectively expressing them in the intestinal epithelium, they won't bother our red blood cells.