Immunomodulation by intravenous immunoglobulin: role of regulatory T cells.

An altered immune homeostasis as a result of deficiency or defective function of CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) is common in several autoimmune diseases. Hence, therapeutic strategies to render Tregs functionally competent are being investigated. Intravenous immunoglobulin (IVIG) is being increasingly used for the treatment of a wide range of autoimmune and inflammatory diseases. Recent studies have demonstrated that IVIG induces the expansion of Tregs and enhances their suppressive functions. These effects of IVIG on Tregs correlate with the beneficial effects of IVIG in patients with autoimmune diseases. Thus, modulation of Tregs by IVIG represents a novel mode of action that explains the therapeutic effects of IVIG in T cell-mediated autoimmune diseases. However, the molecular mechanisms involved in IVIG-mediated modulation of Tregs are unclear and need further investigation.