Mechanism of action IVIg interacts with a number of different components of the immune system, including cytokines, complement, Fc receptors and several cell surface immunocompetent molecules. IVIg also impacts different effector cells of the immune system (B and T lymphocytes, dendritic cells, etc.) and regulates a wide range of genes. Its main mechanism of actions are believed to be Fc-dependent and F(ab')2-dependent. IVIg competitively blocks gamma Fc receptors, preventing the binding and ingestion of phagocytes and suppressing platelet depletion. IVIg contains a number of different antobodies, which prevent infection by attaching to the surface of invading pathogens and aiding in their disposal before they can infect cells. Antibodies remove pathogens via complement activation, agglutination or precipitation, pathogen receptor blocking, macrophage �tagging� or neutralization (via binding) of pathogen toxins.