Anti-idiotype antibodies to anti-myeloperoxidase autoantibodies in patients with systemic vasculitis.

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.