Does the CDR3 of the Heavy Chain Determine the Specificity of Autoantibodies in Systemic Lupus Erythematosus?

Abstract

Many factors are involved in the recognition of autoantigens by autoanti-bodies, including the use of specific germline genes, the sequence and structure of the CDR3 of the heavy chain, somatic mutation and selective heavy and light chain pairing. However, the relative importance of these factors remainsunclear. This study reports the results of sequence analysis of two anti-endothelial cell antibodies that recognise the same antigen. Sequence analysis of these antibodies shows that they use the same heavy chain germline genes as two anti-DNA antibodies but differ significantly in the sequence of the CDR3. Furthermore, one of the antibodies uses a light chain germline gene combination that has been reported for three anti-DNA antibodies. One of these antibodies shows significant mutation in the CDR2 of the heavy chain. Peptide analysis suggests that the differences between these anti-DNA and anti-endothelial cell antibodies result in consistent structural differences that may reflect the nature of the antigen recognised.