Single-cell sequencing on PBMCs from HA & HB patients with inhibitors reveals different immune responses to FVIII & FIX Open Access

• Single-cell sequencing reveals differential immune responses to FVIII and FIX in HA and HB patients.

• B cells are relatively more active in HA patients, while T cells are relatively more active in HB patients when inhibitors are developed.

Inhibitors are the most severe complication of replacement therapy in hemophilia patients. Previous studies, along with our clinical observations, have identified distinct incidence rates and clinical manifestations of factor VIII (FVIII) and factor IX (FIX) inhibitors in patients with severe hemophilia A (HA) and severe hemophilia B (HB). In order to explore different immune responses to FVIII and FIX in HA and HB patients and to elucidate the mechanisms underlying the varying clinical manifestations of these patients, we performed single-cell sequencing on peripheral blood mononuclear cells (PBMCs) collected from five HA and five HB patients with inhibitors. After quality control, a total of 75,051 cells were clustered into 19 subsets. Transcriptome analysis revealed differences in the composition of lymphocyte subsets and the functional status of immune cells between the HA and HB groups. Additionally, immune repertoire analysis indicated variations in the diversity of B and T cell clones between the two groups. HA group exhibited a relatively higher proportion of B cells and more active B cells, whereas HB group demonstrated a higher proportion of T cells, with more active CD4+ T helper (Th) cells. Our study provides insights into the distinct biological processes underlying the distinct immune responses to therapeutic FVIII and FIX in HA and HB patients, as revealed through single-cell sequencing of PBMCs from hemophilia patients with inhibitors. The data generated will serve as a valuable resource for future research on how the immune system recognizes and initiates responses to antigens with varying molecular characteristics.