Contribution of VH Replacement Products to the Generation of Autoreactive Antibodies in Systemic Lupus Erythematosus (129.4)

Abstract

Abstract Systemic lupus erythematosus (SLE) is characterized by the production of high affinity autoantibodies against various nuclear antigens. To gain insight into the mechanisms of autoantibody generation during the course of SLE, we performed single cell PCR analysis and obtained about 200 IgH genes with paired Igκ or Igλ genes from the plasma cells (CD19lowCD27high) and naïve B cells (CD19+CD27−) of three SLE patients. The SLE derived IgH genes have longer CDR3 regions with enriched Arg residues, which are the common features of autoantibodies. SLE plasma cells derived IgH and IgL genes are highly mutated, indicating their positive selection and active involvement in the abnormal immune responses. Interestingly, analyses of the IgL and IgH genes derived from SLE patients showed signs of excessive secondary recombination when compared with those from healthy donors, such as elevated usages of downstream Jκ4, Jκ5, and Jλ3 genes in the IgL genes and concurrently, significantly elevated frequencies of VH replacement products in the IgH genes derived from SLE patients. All the VH replacement “footprints” preferentially contribute charged amino acids into the IgH CDR3 regions. Initial testing of 12 recombinant antibodies derived from SLE plasma cells showed seven of them recognize peri-nuclear antigens. Importantly, the identified VH replacement products directly encode autoantibodies. These findings revealed for the first time that excessive secondary recombination occurred on both IgL and IgH genes in SLE patients and the enriched VH replacement products in SLE plasma cells directly encode autoantibodies.