Fig. 4

a Relationship between IgG and OI responses after PPSV23 vaccination. The 6B serotype-specific IgG (X axis) and OIs (Y axis) responses were plotted in the comparison of three groups (control, MTX, ABT). Positive OI responses were demonstrated in patients receiving ABT with negative IgG responses. b Comparisons of means of OIs between patients with negative or positive serotype 6B-specific IgG responses among three treatment groups (control, MTX, ABT). Error bars represent SD of mean OIs. There was no significant difference in mean OIs between patients with or without positive serotype-6B-specific IgG response in ABT group. IgG immunoglobulin G, OIs opsonization indices, MTX methotrexate, ABT abatacept, SD standard deviation