 One distinct possibility is that sperm and eggs are recognized via oligosaccharides expressed on their surfaces.For example, human gametes are coated with carbohydrate sequences that have been implicated in the suppression of NK cell mediated responses.One of the major corollaries of the eu-FEDS hypothesis is that persistent pathogens and aggressive tumor cells are able to either mimic or acquire the same carbohydrate functional groups used to suppress any immune response that could interfere with the reproductive imperative, thus enabling them to similarly resist the human immune response.