However, emerging evidence suggests that the reported increase in IgG4 levels detected after repeated vaccination with the mRNA vaccines may not be a protective mechanism; rather, it constitutes an immune tolerance mechanism to the spike protein that could promote unopposed SARS-CoV2 infection and replication by suppressing natural antiviral responses. Increased IgG4 synthesis due to repeated mRNA vaccination with high antigen concentrations may also cause autoimmune diseases, and promote cancer growth and autoimmune myocarditis in susceptible individuals.

然而，新出现的证据表明，重复接种 mRNA 疫苗后检测到的 IgG4 水平升高可能不是一种保护机制；相当，它构成了对刺突蛋白的免疫耐受机制，可以通过抑制自然抗病毒反应来促进不受对抗的 SARS-CoV2 感染和复制。由于反复进行高抗原浓度的 mRNA 疫苗接种，导致 IgG4 合成增加，也可能引起自身免疫性疾病，并促进易感个体的癌症生长和自身免疫性心肌炎。

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10222767/#:~:text=However%2C%20emerging%20evidence%20suggests%20that,CoV2%20infection%20and%20replication%20by

IgG4, the least represented human IgG subclass in serum, is an intriguing antibody with unique biological properties, such as the ability to undergo Fab-arm exchange and limit immune complex formation. The lack of effector functions, such as antibody-dependent cell-mediated cytotoxicity and complement-dependent cytotoxicity, is desirable for therapeutic purposes. IgG4 plays a protective role in allergy by acting as a blocking antibody, and inhibiting mast cell degranulation, but a deleterious role in malignant melanoma, by impeding IgG1-mediated anti-tumor immunity. These findings highlight the importance of understanding the interaction between IgG4 and Fcγ receptors.

IgG4 是血清中代表性最少的人类 IgG 亚类，是一种有趣的抗体，具有独特的生物学特性，例如能够进行 Fab 臂交换并限制免疫复合物形成。缺乏效应功能，例如抗体依赖性细胞介导的细胞毒性和补体依赖性细胞毒性，对于治疗目的来说是理想的。IgG4 通过充当阻断抗体并抑制肥大细胞脱粒，在过敏中发挥保护作用，但通过阻碍 IgG1 介导的抗肿瘤免疫，在恶性黑色素瘤中发挥有害作用。这些发现强调了了解 IgG4 和 Fcγ 受体之间相互作用的重要性。

https://pubmed.ncbi.nlm.nih.gov/26497518/#:~:text=IgG4%2C%20the%20least%20represented%20human,and%20limit%20immune%20complex%20formation.

Immunoglobulin G4-related disease (IgG4-RD) is a chronic immune-mediated fibroinflammatory disorder that often manifests with tumor-like masses and/or painless enlargement of multiple organs. Serum IgG4 level is often but not always elevated. Symptoms depend on which organs are affected. Diagnosis generally requires biopsy. Treatment is with corticosteroids and sometimes rituximab.

免疫球蛋白 G4 相关疾病 (IgG4-RD) 是一种慢性免疫介导的纤维炎症性疾病，通常表现为肿瘤样肿块和/或多器官无痛性肿大。血清 IgG4 水平经常但并不总是升高。症状取决于受影响的器官。诊断一般需要活检。治疗方法是使用皮质类固醇，有时使用利妥昔单抗。

https://www.merckmanuals.com/en-ca/professional/musculoskeletal-and-connective-tissue-disorders/igg4-related-disease/igg4-related-disease#:~:text=Immunoglobulin%20G4%2Drelated%20disease%20(IgG4,often%20but%20not%20always%20elevated.