Department of Pathology and Laboratory Medicine, Center for Transfusion Medicine and Cellular Therapies, Emory University School of Medicine, Atlanta, GA, United States.
Aflac Cancer and Blood Disorders Center at Children's Healthcare of Atlanta and Department of Pediatrics, Emory University School of Medicine, Atlanta, GA, United States.
Front Immunol. 2020 Jun 9;11:905. doi: 10.3389/fimmu.2020.00905. eCollection 2020.
Anti-factor VIII (fVIII) alloantibodies, which can develop in patients with hemophilia A, limit the therapeutic options and increase morbidity and mortality of these patients. However, the factors that influence anti-fVIII antibody development remain incompletely understood. Recent studies suggest that Fc gamma receptors (FcγRs) may facilitate recognition and uptake of fVIII by recently developed or pre-existing naturally occurring anti-fVIII antibodies, providing a mechanism whereby the immune system may recognize fVIII following infusion. However, the role of FcγRs in anti-fVIII antibody formation remains unknown. In order to define the influence of FcγRs on the development of anti-fVIII antibodies, fVIII was injected into WT or FcγR knockout recipients, followed by evaluation of anti-fVIII antibodies. Anti-fVIII antibodies were readily observed following fVIII injection into FcγR knockouts, with similar anti-fVIII antibody levels occurring in FcγR knockouts as detected in WT mice injected in parallel. As antibodies can also fix complement, providing a potential mechanism whereby anti-fVIII antibodies may influence anti-fVIII antibody formation independent of FcγRs, fVIII was also injected into complement component 3 (C3) knockout recipients in parallel. Similar to FcγR knockouts, C3 knockout recipients developed a robust response to fVIII, which was likewise similar to that observed in WT recipients. As FcγRs or C3 may compensate for each other in recipients only deficient in FcγRs or C3 alone, we generated mice deficient in both FcγRs and C3 to test for potential antibody effector redundancy in anti-fVIII antibody formation. Infusion of fVIII into FcγRs and C3 (FcγR × C3) double knockouts likewise induced anti-fVIII antibodies. However, unlike individual knockouts, anti-fVIII antibodies in FcγRs × C3 knockouts were initially lower than WT recipients, although anti-fVIII antibodies increased to WT levels following additional fVIII exposure. In contrast, infusion of RBCs expressing distinct alloantigens into FcγRs, C3 or FcγR × C3 knockout recipients either failed to change anti-RBC levels when compared to WT recipients or actually increased antibody responses, depending on the target antigen. Taken together, these results suggest FcγRs and C3 can differentially impact antibody formation following exposure to distinct alloantigens and that FcγRs and C3 work in concert to facilitate early anti-fVIII antibody formation.
抗凝血因子 VIII (fVIII) 抗体可在患有血友病 A 的患者中产生，这会限制治疗选择，并增加这些患者的发病率和死亡率。然而，影响抗 fVIII 抗体产生的因素仍不完全清楚。最近的研究表明，Fcγ 受体 (FcγR) 可能有助于新近产生或预先存在的天然抗 fVIII 抗体识别和摄取 fVIII，为免疫系统在输注后可能识别 fVIII 提供了一种机制。然而，FcγR 在抗 fVIII 抗体形成中的作用尚不清楚。为了确定 FcγR 对抗 fVIII 抗体形成的影响，将 fVIII 注入 WT 或 FcγR 敲除受体中，然后评估抗 fVIII 抗体。在 FcγR 敲除受体中，fVIII 注射后很容易观察到抗 fVIII 抗体，并且在 FcγR 敲除受体中检测到的抗 fVIII 抗体水平与平行注射的 WT 小鼠中检测到的水平相似。由于抗体也可以固定补体，这为抗 fVIII 抗体可能独立于 FcγR 通过影响抗 fVIII 抗体形成提供了一种潜在机制，因此还将 fVIII 平行注入补体成分 3 (C3) 敲除受体中。与 FcγR 敲除受体类似，C3 敲除受体对 fVIII 产生了强烈的反应，其反应与 WT 受体相似。由于 FcγR 或 C3 可能在仅缺乏 FcγR 或 C3 的受体中相互补偿，因此我们生成了同时缺乏 FcγR 和 C3 的小鼠，以测试抗 fVIII 抗体形成中潜在的抗体效应物冗余。将 fVIII 注入 FcγR 和 C3 (FcγR×C3) 双重敲除受体中同样诱导了抗 fVIII 抗体。然而，与单个敲除受体不同，FcγR×C3 敲除受体中的抗 fVIII 抗体最初低于 WT 受体，尽管在进一步暴露于 fVIII 后，抗 fVIII 抗体增加到 WT 水平。相比之下，将表达不同同种异体抗原的 RBC 注入 FcγR、C3 或 FcγR×C3 敲除受体中，与 WT 受体相比，既不能改变抗 RBC 水平，也不能实际上增加抗体反应，具体取决于靶抗原。总之，这些结果表明，FcγR 和 C3 可以在接触不同同种异体抗原后对抗体形成产生不同的影响，并且 FcγR 和 C3 协同作用以促进早期抗 fVIII 抗体形成。
