IFNα antiviral activities and IL-6 immunoreactivities in sera before and after IgG therapy. Left panel, serum antiviral activities before and after IgG administration. Eight of 15 sera did not have detectable antiviral activity before or after IgG (not shown). Horizontal bars show the median values before and after IgG; P < .02. Right panel, Serum IL-6 levels before and after IgG. All sera contained detectable IL-6 when assayed by high-sensitivity ELISA. Horizontal bars show the median values before and after IgG; the difference is not significant.