Effect of anti-GM-CSF treatment on CII-specific immune responses. (a) IgG Ab response to CII measured at the end of each experiment. Results are expressed as the mean ? SEM, where the mean level of anti-CII IgG for isotype control-treated mice was set at 100 U/ml for each experiment and compared with anti-GM-CSF-treated mice from the same experiment. (b) Proliferative response to CII measured in mice treated in vivo with 300 ?g of anti-GM-CSF or control mAb from every second day from days 21 to 31. (c) Proliferative response to CII measured in mice treated in vivo with control mAb, as in (b), except cells were cultured in the presence of 100 ?g/ml anti-GM-CSF or control mAb. (b), (c) Results are shown for cells cultured in the presence of 50 ?g/ml CII, and are expressed as a stimulation index (mean ? SEM) above background readings in the absence of CII (Stimulation Index = 1). CII, type II collagen; GM-CSF, Granulocyte macrophage-colony stimulating factor; mAb, monoclonal antibody.