A diverse array of surface carbohydrate antigens can be found on resident microbes in mammalian hosts. In Nature Chemical Biology, Stowell et al. describe microbial glycan microarrays that consist of defined capsular and lipopolysaccharide antigens, which they use to investigate the recognition properties of host molecules of the innate and adaptive immune systems in serum obtained from humans, mice and rabbits. As expected, antibodies are able to specifically recognize foreign glycan moieties with relatively high affinity. Unexpectedly, several galectins show distinct specificity for self-like carbohydrate structures, including α-galactose, which allows direct recognition and killing of bacteria that express glycans containing these determinants. How galectins can mediate the killing of microbes while sparing host cells that bear similar carbohydrate moieties remains unknown; however, this innate recognition pathway helps prevent evasion of the immune response by molecular mimicry.

Nat. Chem. Bio. 10, 470–476 (2014)