The presence of serum autoantibodies in periodontitis (P) patients against β1-adrenoceptor (β1-AR), using cardiac membranes or a synthetic β1-AR peptide corresponding to the second extracellular loop of human β1-AR as antigens, permit us to detect circulating antibody from 40 P patients but not in 20 normal individuals (control). This evidence concerns the gene ADRB1 and periodontitis.