Immunologic effects of anti‐D (WinRho‐SD) in children with immune thrombocytopenic purpura

Intravenous immunoglobulin (IVIG) is an effective treatment for immune thrombocytopenic purpura (ITP) that induces transient blockade of the reticuloendothelial system (RES) with additional effects including alteration of T lymphocyte subsets and suppression of in vitro T lymphocyte proliferation. As anti‐D also is an effective treatment for ITP, we investigated its in vitro and in vivo immunologic effects. The in vitro effects of various agents used in ITP therapy were compared using T lymphocyte proliferation assays. Anti‐D caused significantly less inhibition than IVIG or dexamethasone, but non‐specific protein was as suppressive as IVIG. Six children with chronic ITP were studied following anti‐D administration. Patients received a single dose of anti‐D (WinRho‐SD, 50 μg/kg IV over 5 min) and were studied on day 0, day 7, and 1 month later. Anti‐D did not affect T lymphocyte subsets including the T cell receptor variable beta repertoire, in vitro T lymphocyte proliferation to mitogens, recall antigens, or interleukin‐2, in vitro IgG synthesis induced by pokeweed mitogen, or T lymphocyte cytokine mRNA levels. We conclude that anti‐D has no demonstrable in vitro or in vivo effects on lymphocyte enumeration or function, and therefore likely is effective in the treatment of ITP primarily through RES blockade. Am. J. Hematol. 57:131–138, 1998. © 1998 Wiley‐Liss, Inc.