HLA-C and infection: To test whether the H-2 locus contributes to immunity we compared secondary infections in C57BL/10 (B10) and C57BL/10.A (B10.A) mouse strains, the latter carrying the MHC H-2 locus of A/J (H-2a) in place of C57BL/6’s MHC H-2 (H-2b).