Interestingly, although MHCI/CD8 deficient mice (B2m) were still protected against a subsequent infection, the difference between Lp thyA and Mock-infected MhcII—/— (CD 4 KO, Ciita) mice was half log smaller in relation to the difference observed in C57BL/6 mice (Fig. 5B). This evidence concerns the gene CIITA and infection.