Thereupon, our group investigated RA-associated autoantibodies in the GCF and serum of patients with RA and healthy controls with or without PD [17] and found that, whereas all autoantibodies including IgA ACPA in GCF of patients with RA were highly correlated with autoantibodies in serum, IgA-ACPA in the GCF of HC was not correlated with systemic levels, but related to inflammation and smoking. The gene discussed is PRTN3; the disease is rheumatoid arthritis.