Anti-Idiotype Antibodies to Anti-Myeloperoxidase Autoantibodies in Patients With Systemic Vasculitis

Abstract The presence of anti-idiotype antibody (anti-id) activity to anti-myeloperoxidase autoantibodies (anti-MPO) was measured by assessing binding of IgG in patients' sera to F(ab′) 2 fragments of polyclonal heterologous anti-MPO antiserum. Thirteen paired acute and remission sera and three groups of sequential sera from patients with systemic vasculitis were studied. The levels of anti-MPO fell as disease activity subsided with treatment. However, levels of anti-id activity against these anti-MPO rose as patients entered remission. This effect was still seen after controlling for binding to F(ab′) 2 constant regions and after polyethylene glycol precipitation of immune complexes. In the sequential studies, levels of anti-MPO and anti-MPO anti-id tended towards a reciprocal relationship. These observations point to dynamic interactions between autoantibody and complementary anti-idiotype antibodies in this system and a role for idiotypic networks in the regulation of anti-neutrophil cytoplasm antibodies.