Interaction of IVIg with Treg and Tconv cells. Single-cell suspension was prepared from the spleen and the LN of C57BL/6J mice and incubated for 45 minutes at 4°C with 10 mg/mL of IVIg or monoclonal M protein (IgG purified from the serum of Multiple Myeloma patients). IVIg binding was revealed using a PE-conjugated antihuman IgG. (A) Lymphocytes were first gated on CD4⁺ T cells that were further gated on (B) CD25⁻ Foxp3⁻ as Tconv and CD25⁺Foxp3⁺ as Treg. (C) Binding of IVIg to the CD4⁻ cells and CD4⁺ cells was analyzed based on MFI. (D) Within CD4⁺ cells, binding of IVIg to Treg and Tconv cells. At the same concentration, monoclonal M protein did not bind to the cells. (E) Treg incubated with or without IVIg.