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 trafficking protein particle complex subunit 4 (TRAPPC4) as a key autoantigen in IRP, including epitope identification and immune activation mechanisms.

Materials and methods: A total of 90 participants were included in the study, divided into four groups: 30 newly diagnosed IRP patients, 25 patients with IRP in remission, 20 patients with other hematological conditions (severe aplastic anemia [SAA] and myelodysplastic syndrome [MDS]) as a patient control group, and 15 healthy individuals as a healthy control group. TRAPPC4 was identified using affinity screening with a phage-display 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 assay, and real-time polymerase chain reaction. Immune cell profiling of peripheral blood mononuclear cells was conducted using flow cytometry.

Results: TRAPPC4 was overexpressed in the CD34+ bone marrow hematopoietic progenitor cells of newly diagnosed IRP patients compared to patients in remission, the patient control group (SAA and MDS), and the healthy control group, with no significant differences observed for 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 to controls. Immune profiling revealed increased CD19+ and CD5+CD19+ B lymphocytes in IRP patients.

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