The 70 kD subunit of the Ku70/Ku80 heterodimer (Ku86), Ku70/XRCC6, was identified by isolation of an antibody from patients with autoimmune thyroid disease and lupus erythematosus, and these antibodies were later used to isolate cDNA clones encoding p70 [135]. The gene discussed is XRCC5; the disease is autoimmune thyroid disease.