Increased serum IgG levels in chronic HCV infection. A, Serum samples (n = 10 healthy control subjects and n = 42 chronic HCV-infected subjects) were analyzed for total human IgG by ELISA. B, Negatively selected bulk B cells (5 × 104 or 1 × 105 as marked on x-axis) were analyzed for total IgG ASC frequency after 4 d culture with CpG 2006 (2.5 μg/ ml) and SAC (1:10,000) (n = 14 healthy controls and n = 14 HCV-infected subjects shown). C, Tetanus-specific IgG ASC (n = 13 healthy controls and n = 14 HCV-infected subjects shown). D, HCV-specific (HCV core, NS3, or NS4 recombinant protein) ASC (n = 11 healthy controls and n = 13 HCV-infected subjects shown).