The defective IL-12 response in C57BL/10ScCr mice has been attributed to a point mutation in the Il12rb2 gene. The substitution of a C to G at coding nucleotide 2331 creates a premature stop codon at tyrosine amino acid position 778 (p.Y778*). The resulting truncated protein lacks the C-terminal 96 amino acids of cytosplasmic domain.