Ferritin Light Chain: A Candidate Autoantigen in Immuno-Related Pancytopenia

The characteristic feature of immune-related pancytopenia (IRP) is autoantibody-mediated bone marrow (BM) damage and peripheral blood cytopenia. We found that the potential antigen of IRP was Ferritin light chain (FTL) by SEREX (serological analysis of recombinant cDNA expression libraries) in the previous study. In this study, we tried to explore the antigenic epitopes of FTL and verify its antigenicity in IRP. We found the possible FTL epitope: VNLYLQASYTYLSLG by phage random peptide library. Through ELISPOT, it was found that peptide VNLYLQASYTYLSLG can significantly stimulate the production of interleukin-4 and cannot stimulate the production of interferon-γ, which suggested that the peptide can obviously activate Th2 cells. Peptide–major histocompatibility complex tetramer elicited antigen-specific T cell responses. The expression levels of FTL were significantly increased in the patients with untreated IRP (P < 0.05). In conclusion, we found that FTL is the target antigen for some patients with IRP. The peptide of VNLYLQASYTYLSLG is an epitope of the target antigen. The target antigen is abnormally overexpressed on the membrane of BM cells, especially on the surface of CD34+ BM cells of patients with IRP. In addition, it is related to the severity of disease. These results provide a possible new target for the treatment of IRP in the future.