Fig. 4.

Reduced antibody levels after treatment with abatacept in the absence of CD4⁺ T cells. Antibody levels were determined by enzyme-linked immunosorbent assay over time. Serum samples were collected on days 0, 12, 21, 22, 35 and 47/48 after the start of treatment, and total IgG2a and IgG1 levels were determined in the thymectomized mice. In addition, bovine and mouse collagen type II–specific IgG2a and IgG1 levels were determined. a Levels are depicted as percentages of day 0. b An independent experiment including the isotype for abatacept. Abatacept-only treatment is not depicted to improve the readability of the graphs, but it showed results comparable to those for abatacept + CD4 depletion. Levels are depicted as percentages of day 0. Values are mean ± SEM (n=10 per treatment group). Statistical analysis was performed using the Mann–Whitney U test. *P < 0.05 abatacept + CD4 depletion vs control group. AU arbitrary units, bCII bovine collagen type II, CII collagen type II, IgG immunoglobulin G, mCII mouse collagen type II, PBS phosphate-buffered saline