IL15 and fetal growth restriction: Mice devoid of uNK cells, like IL-15 KO mice that do not have NKs or uNK cells, have impaired SA modification and placenta development, resulting in intrauterine growth restriction (IUGR) and smaller progeny (80), but it has to be kept in mind that in addition to NK deficiency IL-15 KO mice display other impairments, which may affect pregnancy.