SSB and systemic lupus erythematosus: Existing evidence supports a model for anti-Ro (in those patients who do not also develop anti-La) [20] involving Epstein-Barr virus Nuclear Antigen-1 (EBNA-1) as the cross-reacting hetero-antigen that mediates the antibody cross-reaction making 60 kD Ro an initiating lupus autoantigen [20].