FIG. 4.
Frequency of spontaneously secreting IgG AFCs in adults after a single dose of Pnc7 (triangles) and 12-month-old toddlers after a single dose (closed circles) and a second dose (open circles) of Pnc7. PBMCs were isolated prior to and 1 week after each dose of vaccine and were allowed to spontaneously secrete IgG onto ELISPOT assay plate wells coated with the control antigen (tetanus toxoid [tet]) and the vaccine antigens (diphtheria toxoid [dip] and polysaccharide serotypes 4, 14, and 23F). The spots were enumerated and expressed as the numbers of IgG AFCs/106 PBMCs, and the bars represent the medians (***, P ⩽ 0.0001).