Rabies-specific IgG, IgA, IgM plasma-cell and IgG memory B-cell responses after immunization of naive and immune volunteers. The naive volunteers (left) were immunized at days 0, 28, and 56, and the frequencies of rabies IgG- (A), IgA- (B), and IgM-specific (C) plasma cells (PCs) and IgG memory B-cells (MCs; D) were measured at various days after the first and third doses of immunization. The immune volunteers (right) were immunized at day 0, and the frequencies of rabies IgG- (E), IgA- (F), IgM-specific PCs (G), and IgG MCs (H) were measured at various days after immunization. The horizontal bars represent the median number of specific antibody-secreting cells at each time point. The minimum sensitivity of the assay is plotted as a broken line on the graphs for each figure. The zero values were assigned a value of 1 for illustrative purposes. The magnitude of the IgG PC response after booster immunization in the immune group was greater than after primary and tertiary immunization in the naive group. However, the magnitude of the IgG MC response after booster immunization in the immune group was greater than after primary and secondary immunization but not tertiary immunization.