Human intravenous immune globulin (IVIg), a purified IgG fraction composed of similar to 60% IgG1 and obtained from the pooled plasma of thousands of donors, is clinically used for a wide range of... Show moreHuman intravenous immune globulin (IVIg), a purified IgG fraction composed of similar to 60% IgG1 and obtained from the pooled plasma of thousands of donors, is clinically used for a wide range of diseases. The biological actions of IVIg are incompletely understood and have been attributed both to the polyclonal antibodies therein and also to their IgG (IgG) Fc regions. Recently, we demonstrated that multiple therapeutic human IgG1 antibodies suppress angiogenesis in a target-independent manner via FcyRI, a high-affinity receptor for IgG1. Here we show that IVIg possesses similar anti-angiogenic activity and inhibited blood vessel growth in five different mouse models of prevalent human diseases, namely, neovascular age-related macular degeneration, corneal neovascularization, colorectal cancer, fibrosarcoma and peripheral arterial ischemic disease. Angioinhibition was mediated by the Fc region of IVIg, required FcyRl and had similar potency in transgenic mice expressing human FcyRs. Finally, IVIg therapy administered to humans for the treatment of inflammatory or autoimmune diseases reduced kidney and muscle blood vessel densities. These data place IVIg, an agent approved by the US Food and Drug Administration, as a novel angioinhibitory drug in doses that are currently administered in the clinical setting. In addition, they raise the possibility of an unintended effect of IVIg on blood vessels. Show less
Bogdanovich, S.; Kim, Y.; Mizutani, T.; Yasuma, R.; Tudisco, L.; Cicatiello, V.; ... ; Ambati, J. 2016
Aberrant angiogenesis is implicated in diseases affecting nearly 10% of the world's population. The most widely used anti-angiogenic drug is bevacizumab, a humanized IgG1 monoclonal antibody that... Show moreAberrant angiogenesis is implicated in diseases affecting nearly 10% of the world's population. The most widely used anti-angiogenic drug is bevacizumab, a humanized IgG1 monoclonal antibody that targets human VEGFA. Although bevacizumab does not recognize mouse Vegfa, it inhibits angiogenesis in mice. Here we show bevacizumab suppressed angiogenesis in three mouse models not via Vegfa blockade but rather Fc-mediated signaling through Fc gamma RI (CD64) and c-Cbl, impairing macrophage migration. Other approved humanized or human IgG1 antibodies without mouse targets (adalimumab, alemtuzumab, ofatumumab, omalizumab, palivizumab and tocilizumab), mouse IgG2a, and overexpression of human IgG1-Fc or mouse IgG2a-Fc, also inhibited angiogenesis in wild-type and Fc gamma R humanized mice. This anti-angiogenic effect was abolished by Fcgr1 ablation or knockdown, Fc cleavage, IgG-Fc inhibition, disruption of Fc-Fc gamma R interaction, or elimination of FcR gamma-initated signaling. Furthermore, bevacizumab's Fc region potentiated its anti-angiogenic activity in humanized VEGFA mice. Finally, mice deficient in Fc gamma RI exhibited increased developmental and pathological angiogenesis. These findings reveal an unexpected anti-angiogenic function for Fc gamma RI and a potentially concerning off-target effect of hIgG1 therapies. Show less
