Identification of TRAPPC4 as a Key Autoantigen in Immune-Related Pancytopenia: Epitope Characterization and Immune Activation Mechanisms.

Abstract

Objective: Immune-related pancytopenia (IRP) is characterized by autoantibody-mediated destruction or suppression of bone marrow cells, leading to pancytopenia. This study aimed to explore the role of TRAPPC4 (trafficking protein particle complex subunit 4) as a key autoantigen in IRP, including epitope identification and immune activation mechanisms.

Methods: A total of 90 participants were included in the study, divided into four groups: 30 newly diagnosed IRP patients, 25 IRP remission patients, 20 patients with control hematologic conditions (severe aplastic anemia [SAA] and myelodysplastic syndrome [MDS]), and 15 healthy controls. TRAPPC4 was identified using affinity screening with a phage random peptide library and confirmed with ELISPOT and epitope prediction software. TRAPPC4 expression in bone marrow cells and serum antibody titers was assessed via flow cytometry, ELISA, and real-time PCR. Immune cell profiling of peripheral blood mononuclear cells (PBMNCs) was conducted using flow cytometry.

Results: TRAPPC4 was overexpressed on CD34+ bone marrow hematopoietic progenitor cells in newly diagnosed IRP patients compared to remission patients, disease controls (SAA and MDS), and healthy controls, with no significant differences observed in CD15+ granulocytes or CD235a+ nucleated red blood cells. The epitope peptide YTADGKEVLEYLG activated Th2 cells, as confirmed by ELISPOT. Newly diagnosed IRP patients exhibited elevated TRAPPC4 mRNA and protein levels in bone marrow mononuclear cells and higher serum antibody titers compared with controls. Immune profiling revealed increased CD19+ and CD5+CD19+ B lymphocytes in IRP patients.

Conclusion: TRAPPC4 was found as a key autoantigen in IRP, along with CD34+ cells as primary targets of autoantibody attacks. The identification of TRAPPC4 and its epitope provided insights into IRP pathogenesis and suggested potential diagnostic and therapeutic strategies.