The objective was to re-evaluate the association between class II
HLA-DR and DQ MIIC
antigens and
postpartum thyroiditis (PPT) and to determine the prevalence of the class III
complement allotypes of
Properdin factor B (Bf), C4A and C4B in this condition. Two hundred and sixty-five (of 2897) pregnant women screened positive for thyroid
autoantibody activity took part. Further blood samples were obtained for HLA class II (185) and
complement (193) typing. The severity of the ensuing PPT was assessed by measuring thyroid function during the postpartum year. The
HLA-DR and DQ phenotypes were assigned from restriction fragment length polymorphism analysis, and Bf, C4A and C4B allotypes were determined by immunofixation with anti-Bf or anti-C4
antibodies after electrophoresis. A weak association between the HLA
class II antigens and PPT, as indicated by a reduced frequency of DR15 and DQ6 together with an increased frequency of-DR5 and DQ7, was confirmed. However, only the change in DR5 frequency remained significant after correction (corrected p < 0.05).
Postpartum thyroiditis was also associated with frequency disturbances in BI and C4A allotypes but not C4B allotypes. Whilst this study has not provided evidence of a strong marker gene for PPT, it does not preclude the involvement of the MIIC in this condition. These data show disturbances in
complement allotype frequencies, suggesting that the class III region may provide a useful focus for further study of this pathology.