Mutant __SP__ B7 1 [__NODE__] gene ( homozygous knockout ) in __SP__ and mutant __SP__ B7 2 [__NODE__] gene ( homozygous knockout ) in __SP__ and mutant __SP__ __NODE__ in __SP__ cause little or no change in localization of __SP__ IgG3 protein [IgG3] in serum from __SP__ .