Anti-D Ig for treatment of immune thrombocytopenic purpura.

In a recent article on the treatment of autoimmune thrombocytopenia (AITP) with anti-D Ig, Bussel et al' make several assertions that we would question. Many preparations of anti-D Ig for intramuscular use contain substantial quantities of polymeric IgG, but this is responsible for most of the inhibitory activity against macrophage Fc receptors and we have shown that the platelet count responses to different anti-D and other therapeutic Igs are porportionate to their polymeric IgG content? Bussel et a1 were unable to show this with the intravenous Winrho product. Most manufacturers of anti-D Ig calibrate the material by adding variable quantities of non-specific IgG, and recent evidence has shown that the responses in ITP are due to this material and not to the anti-D component.'^^ This theory is also supported by the reports of responses in AITP patients who are rhesus-negative," which is contrary to what Bussel et a1 have stated. Shortand long-term responses to anti-D Ig are seen in AITP, and recent work has shown that these responses are due to several mechanisms including monocyte-phagocyte FcR inhibition by polymeric IgG material, and the inhibition of autoimmune antibody synthesis by anti-idiotypic antibodies?.' The latter contrasts with the effects Bussel et a1 describe on IgG synthesis in vitro. Bussel et a1 also make observations concerning the safety of the Winrho anti-D Ig that we think could be misleading. All the original IgG preparations for intramuscular use were manufactured by simple Cohn ethanol fractionation and contained polymeric IgG. Although these caused severe adverse reactions when administered intravenously to patients with hypogammaglobulinemia, this was not so in subjects with normal levels of IgG.9 Most anti (Rh)-D immunoglobulins are manufactured for intramuscular use, but we have now safely administered such preparations by slow intravenous infusion to over 50 patients with AITP without adverse reactions. This contrasts with the five severe reactions described by Bussel et al, who are clearly incorrect in their assertion that the Winrho anti-D is uniquely safe for use in AITP.