Lectins are sugar-binding proteins that are highly specific for their sugar moieties. They play a role in biological recognition phenomena involving cells and proteins. For example, some viruses use lectins to attach themselves to the cells of the host organism during infection. Lectins may be disabled by specific mono- and oligosaccharides which bind to them and prevent their attachment to cell membranes. Lectins were first discovered more than 100 years ago in plants, but they are now known to be present throughout nature. Lectins are also prevalent in the microbial world, wherein they tend to be called by other names, such as hemagglutinins and adhesions