Intravenous immunoglobulin (IVIG)
Intravenous immunoglobulin is the pooled-donor-derived antibody and immunomodulator preparation that, in the Circulate protocol, is infused following therapeutic plasma exchange. IVIG itself is an established clinical product with decades of safety experience in autoimmune neurological and hematologic indications; the novel element is its use for aging-related off-label purposes in combination with TPE. The biological role attributed to IVIG in the aging context (immunomodulation, immune-system rejuvenation, complement and Fc-receptor effects translated from the autoimmune-indication mechanism) is proposed and consistent with IVIG’s known pharmacology, but is not yet supported by trial evidence beyond the single Aging Cell publication, which carries a disclosed conflict of interest (the investigators are members of the commercializing company Circulate, Inc.; the paper states it received no specific funding).