IFNG and viral infectious disease: Nevertheless, the levels of neutralizing antibodies were positively correlated with IgG2a O.D. values in C57BL/6 mice (Figure 9, panels A, C and E) as well as in BALB/c mice (Figure 9 panels B, D and F) while there was no correlation with IgG1 O.Ds (data not shown), showing that IFN-γ might have a role during class switch for antibody production after YF 17D virus infection in mice.