IMMUNE MODULATION ASSOCIATED WITH EXTRACORPOREAL IMMUNOADSORPTION TREATMENTS UTILIZING PROTEIN-A SILICA COLUMNS

The Prosorba column is designed for the removal of IgG and IgG contain ing immune complexes from plasma. Clinical studies employing patients presenting with idiopathic thrombocytopenic purpura (ITP) indicate tha t this new form of therapy is effective in approximately 40% of treate d patients. Responding patients exhibit a significant increase in plat elet numbers associated with decreases in antiplatelet antibody and im mune complexes suggesting the induction of immune modulation. Prelimin ary studies indicate that ITP patients presenting with antiplatelet Ig G antibody are those most likely to respond. In addition, this subgrou p of ITP patients also exhibit elevated levels of antiidiotypic IgG an tibody, which may contribute to an exacerbation of the autoimmune proc ess due to antigen mimicry of the platelet autoantigen. Interestingly, antiidiotypic IgG antibody levels appear to decrease in association w ith antiplatelet IgG autoantibody levels suggesting that removal of im mune complexes composed of IgG autoantibody and platelet autoantigen a nd/or antiidiotypic IgG antibody may be related to the observed clinic al responses. Additional studies with alloimmune patients refractory t o platelet transfusion suggest that transfused platelet retention time may be increased as a consequence of immunoadsorption therapy. This c linical response appears to be related to decreases in IgG alloantibod y, again suggesting the induction of immune modulation. Alloimmune thr ombocytopenic patients also appear to present with elevated levels of antiidiotypic IgG antibody which may contribute to an exacerbation of the alloimmune process due to antigen mimicry of platelet alloantigen( s). Preliminary studies indicate that both IgG alloantibody and corres ponding antiidiotypic IgG antibody levels appear to decrease during im munoadsorption therapy, which suggests that removal of these antibodie s, possibly in the form of immune complexes, may be related to clinica l responses. Finally, studies in rheumatoid arthritis patients suggest that immunoadsorption therapy may be of clinical benefit in this auto immune disorder. Consistent with the results observed above, prelimina ry studies in patients responding to immunoadsorption treatments again suggest that there is a concomitant decrease in idiotypic IgG (rheuma toid factor) and antiidiotypic IgG antibodies levels during therapy.