Significantly higher levels of anti-MmuPV1 E4 IgG3 antibody were detected in all infected NU/J heterozygous mice initiated with different doses of viral infection, compared to those in Rag1ko mice (indicated by a square), at dilutions ranging from 1:100 to 1:1,000 (B, P < 0.05, one-way ANOVA) (27, 40). The gene discussed is IGHG3; the disease is viral infectious disease.