Immune Globulin (Human), Intravenous (IVIG)

**Immune Globulin (Human), Intravenous (IVIG)** is a highly concentrated biological product consisting of fractionated immunoglobulins (primarily IgG) pooled from thousands of human plasma donors. In veterinary medicine, it is primarily utilized as an expensive, off-label **salvage therapy** for severe, refractory immune-mediated diseases when conventional immunosuppressive therapies (like glucocorticoids or cyclosporine) have failed. **Key Clinical Applications:** * **Primary Immune-Mediated Thrombocytopenia (pIMT):** Shows the most promise in veterinary studies for rapid platelet recovery. * **Immune-Mediated Hemolytic Anemia (IMHA):** Used in refractory cases, though prospective studies show mixed results regarding survival benefits compared to standard therapy. * **Immune-Mediated Dermatopathies:** E.g., Erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis. > **Clinical Pearl:** Because IVIG is a human blood product, its use in veterinary medicine is controversial due to ethical considerations regarding human supply shortages, the extremely high cost of the drug, and the risk of hypersensitivity reactions to foreign proteins.

กลไกการออกฤทธิ์: IVIG exerts complex immunomodulatory effects through multiple concurrent pathways rather than a single mechanism: * **Fc Receptor Blockade:** The massive influx of human IgG binds to and saturates **Fc receptors** on the patient's mononuclear phagocyte system (macrophages) → prevents the phagocytosis and destruction of the patient's own autoantibody-coated red blood cells or platelets. * **Anti-idiotypic Antibodies:** Contains antibodies that directly bind to and neutralize pathogenic autoantibodies. * **Cytokine Modulation:** Binds to and downregulates pathogenic cytokines including **Interleukin (IL)-1a**, **IL-6**, and **Tumor Necrosis Factor-alpha (TNF-α)**. * **Receptor Interference:** Binds to **CD5 receptors** and **T-cell receptors**, suppressing pathogenic T-cell and B-cell activation. * **Negative Feedback:** High circulating IgG levels provide negative feedback → downregulation of endogenous antibody production by B lymphocytes.

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