Significant aggravated disease activities, including reduced platelet count, prolonged thrombocytopenia time, increased binding activity of autoantibody, elevated MMP9 activity and protein expression, were observed in NZB/W F1 mice that were received anti-B19-VP1u IgG as compared to those mice that were received rabbit control IgG, rabbit anti-B19-NS1 IgG or PBS, respectively. The gene discussed is MMP9; the disease is Thrombocytopenia.