Board Thread:General Discussion/@comment-968312-20150209182531/@comment-26601629-20170905231344

They actually did mention blood types, in all likelihood, all people on the ark were genetically engineered to be universal donors. While the grounders do have bloodtypes, Nyko was stated to be Rh-Null. The Mount Weather thing was most likely a case where they kidnapped so many grounders that they probably had all blood types in there. Afterall, they did take Nyko to Mount Weather to get the Rh Null blood.