Editor's Note: The 32nd International Society on Thrombosis and Haemostasis (ISTH 2024) Congress was held in Bangkok, Thailand, from June 22 to June 26, 2024. As the most influential event in the field of thrombosis and hemostasis, the ISTH Congress attracts thousands of top experts and scholars worldwide with its profound academic impact and rich content. The "ISTH China's Voices" column of Oncology Frontier-Hematology Frontier aims to showcase outstanding research achievements from the Chinese academic community at ISTH. In this issue, we present a research finding from Dr. Enhao Li of Professor Xuefeng Wang's team at Ruijin Hospital, Shanghai Jiaotong University School of Medicine. Dr. Li's oral presentation at ISTH delved into the differential immune responses to FVIII and FIX in hemophilia A (HA) and hemophilia B (HB) patients, providing valuable academic insights for the hematology field.
Single-cell sequencing of PBMCs from hemophilia A and hemophilia B patients with inhibitors reveals different immune responses to FVIII and FIX after replacement therapy
Background
About 30% severe hemophilia A (HA) patients develop FVIII inhibitors due to alloimmune responses following replacement therapy, while only about 10% severe hemophilia B (HB) patients produce inhibitors against FIX after after receiving FIX agents. Additionally, there are significant differences in the sensitivity to the immune suppression therapy for eliminating inhibitors and the relapse rate after eliminating inhibitors between HA and HB patients with inhibitors. The mechanism under the apparent difference of immune reactions upon exposure to administered FVIII and FIX has not been fully appreciated.
Objective
This study aims to explore the differences in immune responses to FVIII and FIX in HA and HB patients and reveal different mechanisms leading to apparently different clinical manifestations of HA and HB patients with inhibitors.
Methods
The study performed single-cell sequencing on PBMCs collected from five HA and five HB patients with inhibitors. After pre-processing the data with “CellRanger”, “Seurat”, “doubletfinder” and “harmony” R packages were applied for quality control and to cluster cell subsets and calculate differentially expressed genes in R 4.2.2. “immunarch” R package was used to analyze the diversity of immune repertoire including B-cell receptor (BCR) and T-cell receptor (TCR) repertoire. Statistical analyses were performed in R 4.2.2.
Results
After quality control of the data, totally 75,051 cells, including 32,679 cells from HA and 42,372 cells from HB, were clustered to 19 subsets according to the markers of each cluster. Student’s t test on cell ratios of different types of immune cells in lymphocytes between two groups showed that HB patients with inhibitors had statistically significantly higher T cell ratio, while HA patients with inhibitors had higher B cell ratio. We found that HA group had relatively more diverse B cell clones, and HB group had relatively more diverse T cell clones but without statistical significance.
Conclusion
Our results support the notion proposed by previous studies suggesting that the immune systems might recognize and initiate alloimmune response to exogenous FVIII and FIX in HA and HB patients through different pathways. The structural difference, tissue distribution and metabolism of intravenously administered FVIII and FIX might be responsible for the apparently different immune reactions underlying inhibitor development in HA and HB patients.
