To the Editor:We thank Trinath et al for their interest in our recently published data on the mechanism of action of intravenous immuno-globulin (IVIg) using our model of allergic airways disease. We demonstrated that allergic airway hyperresponsiveness was abrogated by IVIg via induction of allergen-specific regulatory T cells. The induction of regulatory T cells was dependent on the presence of antigen (ovalbumin [OVA] or ragweed) and could be duplicated by adoptive transfer of dendritic cells (DCs) from mice treated with IVIg. In analyzing both lung digests and isolated pulmonary DCs, we found high Jagged-1 expression following OVA exposure, which was reversed by IVIg. In addition, DCs from OVA-exposed, IVIg-treated mice exhibited increases in Delta-4 expression. Regulatory T-cell induction via modulation of Notch-ligand expression on DCs is one possible explanation for the action of IVIg.
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