HTT and Huntington disease: Here, we generated and characterized an immune deficient and xeno‐tolerant mouse model of Huntington's disease with the human mutated HTT gene by cross‐breeding the NOD.Cg‐PrkdcscidIl2rγtm1Wgl/SzJ (NSG) mouse,18, 19 a well‐known immune deficient model, with YAC128 mice.