IMMUNOGENETICS OF EPITOPES OF THE CARBOXYL-TERMINUS OF THE HUMAN 60-KD RO AUTOANTIGEN

Systemic lupus erythematosus is associated with the presence of autoan tibodies which bind several ribonucleoproteins, including Ro (or SS-A) . We have explored the relationship of the HLA-DQ and T cell receptor alleles in patients producing autoantibodies binding the 13-kD carboxy l terminus fragment of the 60-kD Ro and with autoantibodies binding a peptide epitope within this fragment (amino acid residues 480-494). An tibodies binding the 13-kD fragment are more likely to be found in the sera of patients with particular DQA1 and DQB1 alleles, while antibod ies binding the epitope at 480-494 are found almost exclusively in the sera of patients with a BglII 9.8-kb polymorphism of the T cell recep tor beta gene. Meanwhile, in these same patient sera the level of auto antibodies binding the complete 60-kD Ro particle is associated with a distinct pattern of alleles at these same immunoregulatory loci. Thes e data demonstrate that component parts of autoantibody responses may be under genetic control which can be distinguished from the HLA assoc iations characteristic of the response to the intact, complete autoant igen.