All sequences from the upstream of mouse H2-Ab1 gene exon 2 to the upstream of the H2-Ea-ps gene exon 1 were knocked out to obtain H2-Ab1,H2-Aa,H2-Eb1,H2-Eb2,H2-Ea-ps knockout mouse models. These MHC class II molecule-deficient mice were on the NMG genetic background and also lacked cell surface expression of both class II-A and class II-E MHC proteins.