Predominance of IgG1 and IgG3 subclasses of autoantibodies to peptidylarginine deiminase 4 in rheumatoid arthritis.

Analysis of IgG subclass distribution of antibodies may provide insights into the mechanisms driving antibody production. Here, we have first determined IgG subclass distribution of anti-recombinant peptidylarginine deiminase 4 (anti-hPADI4) antibodies in sera from patients with rheumatoid arthritis (RA). Sera from 103 RA patients were screened to IgG anti-PADI4 using recombinant antigens. For positive samples, the subclass distribution of IgG anti-hPADI4 was determined by means of establishing the equipotency of four HRP-labeled IgG subclass-specific monoclonal antibodies. The subclass profiles were compared among individuals with different disease status. Thirty-three out of 103 RA patients were determined as IgG anti-hPADI4-positive. As expressed by percentage levels to total IgG anti-hPADI4 activity, IgG1 and IgG3 were determined to be the predominant subclasses of anti-hPADI4. Furthermore, distinct subclass distribution patterns were observed in patients with different disease status. The IgG subclass distribution of anti-hPADI4 indicates that a leading T lymphocyte-regulated IgG1 and IgG3 responses may contribute to a better understanding of the role of anti-PADI4 in RA.