Exploration of B- and T-Cell Receptor Repertoires Reveals Distinct Mechanisms in Pure Red Cell Aplasia, Autoimmune Hemolytic Anemia, and Aplastic Anemia.

Introduction: Pure red cell aplasia (PRCA), autoimmune hemolytic anemia (AIHA), and aplastic anemia (AA) are immune-mediated diseases that affect mainly erythrocytes or erythroid progenitor cells. This study aimed to investigate changes related to autoimmunity in B-cell receptor (BCR) and T-cell receptor (TCR) repertoires in patients with these diseases.

Methods: Patients with primary PRCA, AIHA, and AA and normal controls (NCs) were recruited. Peripheral blood was collected, and BCR and TCR repertoires were sequenced by next-generation immunosequencing.

Results: Ten patients with PRCA, 10 with AIHA, 10 with AA, and 7 NCs were ultimately enrolled. According to the broad repertoire metric analysis, only the TCR repertoire of the AA group was more diverse than that of the NC group (p < 0.05). Regarding BCR and TCR repertoires, the PRCA, AIHA, and AA groups had uniform gene characteristics. The preferential gene of immunoglobulin heavy chains in PRCA patients was correlated with memory cell and red blood cell antigen recognition; genes expressed in the AIHA group were associated with the secretion of autoantibodies, whereas AA patients had more genes related to neutralizing antibodies. For T-cell receptor β (TRB) chains, PRCA patients had skewed use of genes associated with T-cell dysregulation and hyperinflammation, whereas AIHA and AA patients had similar genes as patients with other autoimmune diseases, which correlated with abnormal antigen recognition. PRCA and AA patients had specific TRBV-J gene combinations. For the BCR light chains, PRCA and AIHA patients tended to use more κ chains, whereas AA patients tended to use more λ chains. Regarding the TCRα chains, patients with each of the three diseases expressed more genes related to hypersensitivity reactions (p < 0.05). Compared to the NC group, the PRCA and AIHA groups had greater BCR somatic hypermutation (SHM). The length of CDR3 was similar, but the hydrophobicity differed among the different disease groups. Different motifs were found in BCRs and TCRs of the three diseases. Compared to NCs, the PRCA, AIHA, and AA groups showed a considerable lack of physiological T-cell clusters, and some disease-specific T-cell clusters were found in each disease group.

Conclusion: PRCA, AIHA, and AA patients had different BCR and TCR repertoire characteristics in terms of genes and gene combinations, hydrophobicity and CDR3 motifs, and T-cell clustering, which might contribute to autoimmune antigen recognition. The abnormalities were mainly T-cell related for PRCA patients, B-cell related for AIHA patients and both for AA patients.