Relation of disease subtype and T-cell proliferative responses induced by aggrecan, fibrillin, and matrix metalloproteinase (MMP)-3. Proliferative responses to the aggrecan peptide of peripheral blood mononuclear cells (PBMC) from both oligoarticular and polyarticular juvenile idiopathic arthritis (JIA) patients differed significantly with those from healthy controls (p = 0.034 and p = 0.036, respectively). Only PBMC from patients with polyarticular JIA showed significant T-cell proliferative responses to the fibrillin peptide (p < 0.0001 versus healthy controls, p = 0.003 versus oligoarticular JIA). Positive proliferative responses to the MMP-3 peptide were seen in both JIA subgroups and healthy controls. Black bars: oligoarticular JIA; gray bars: polyarticular JIA; transparent bars: healthy controls. Asterisks indicate significant difference.