Porphyromonas gingivalis immunoglobulin G antibody responses. Porphyromonas gingivalis (Pg) antibody responses are shown in age-similar healthy hospital personnel and blood bank donors, in patients with early or late RA and in patients with other connective tissue diseases (CTDs), including 17 patients with lupus and another group consisting of 10 patients with Sjögren syndrome, 4 with scleroderma and 3 with mixed CTD. (A) All data points are shown for each individual group. (B) The results are summarized, and data from all healthy control participants and patients with CTD or RA are combined. In (B), the histograms give the mean values, and I-bars show the standard error of the mean. The shaded region represents < 2 SD above the mean absorbance of healthy hospital personnel. Abs: absorbance; IgG: immunoglobulin G.