Sneed Sunny L, Strandberg Elizabeth A, Laureano Ana F S, Vattepu Ravi, Sun Yehao, Tran Truc T, Conroy Michelle E, Anthony Robert M
Center for Immunology and Inflammatory Diseases, Division of Rheumatology, Allergy, and Immunology, Department of Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02129.
Proc Natl Acad Sci U S A. 2025 May 20;122(20):e2411600122. doi: 10.1073/pnas.2411600122. Epub 2025 May 16.
IgG antibodies are the basis for many successful therapeutics. A single, N-linked glycan is present on the Fc on all IgGs, and the composition of that glycan exerts marked influence over effector functions of the IgG. We and others have shown terminal sialylation of the Fc glycan confers anti-inflammatory activity to the IgG1 subclass and is thought to be responsible for the anti-inflammatory activity of high-dose intravenous immunoglobulin. However, whether sialylation results in anti-inflammatory activity for other IgG subclasses is unknown. We found that IgG1 and IgG3, but not IgG2 nor IgG4, suppressed autoantibody-mediated inflammation in vivo when sialylated. This activity was dependent upon human DC-SIGN or its murine ortholog, SIGN-R1. Fc γ receptor-binding profiles for asialylated and sialylated IgG subclasses reinforced these similarities, with IgG1 and IgG3 sharing binding patterns. Amino acid sequence alignments identified two uniquely conserved amino acid residues at positions 234 and 327 of the CH2 domain of all human IgG1 and IgG3 allotypes that were distinct from IgG2 and IgG4. Indeed, molecular modeling of the shared residues in IgG1 and IgG3 revealed a hydrophobic-heavy interchain interaction that was not present in IgG2 nor IgG4. Introduction of those IgG1/3 residues into an IgG4-Fc resulted in anti-inflammatory activity in vivo when sialylated. Conversely, a reciprocal sialylated IgG1 mutant with IgG2/4 residues lacked anti-inflammatory activity. These results define the amino acid requirements of anti-inflammatory sialylated IgG and enable rational amino acid and glycan engineering across all therapeutic IgG subclasses.
IgG抗体是许多成功治疗药物的基础。所有IgG的Fc段上都存在一个单一的N-连接聚糖，该聚糖的组成对IgG的效应功能有显著影响。我们和其他人已经表明，Fc聚糖的末端唾液酸化赋予IgG1亚类抗炎活性，并且被认为是高剂量静脉注射免疫球蛋白抗炎活性的原因。然而，唾液酸化是否会导致其他IgG亚类产生抗炎活性尚不清楚。我们发现，唾液酸化的IgG1和IgG3，但不是IgG2和IgG4，在体内可抑制自身抗体介导的炎症。这种活性依赖于人DC-SIGN或其小鼠同源物SIGN-R1。去唾液酸化和唾液酸化的IgG亚类的Fcγ受体结合谱强化了这些相似性，IgG1和IgG3具有共同的结合模式。氨基酸序列比对确定了所有人类IgG1和IgG3同种型的CH2结构域第234和327位有两个独特保守的氨基酸残基，这与IgG2和IgG4不同。事实上，IgG1和IgG3中共享残基的分子模型显示出一种疏水-重链间相互作用，而IgG2和IgG4中不存在这种相互作用。将那些IgG1/3残基引入IgG4-Fc中，唾液酸化时在体内产生抗炎活性。相反，具有IgG2/4残基的相互唾液酸化IgG1突变体缺乏抗炎活性。这些结果确定了抗炎唾液酸化IgG的氨基酸要求，并能够对所有治疗性IgG亚类进行合理的氨基酸和聚糖工程改造。
