Autoantibodies to plasminogen and tissue plasminogen activator in women with recurrent pregnancy loss

Summary Reduced fibrinolytic activity has been described in primary anti‐phospholipid syndrome (PAPS), and may be responsible for thrombotic events. Antibodies to tissue type plasminogen activator (t‐PA) or plasminogen (PLG) might contribute to the hypofibrinolytic state in autoimmune diseases, but the clinical significance of these antibodies is still unclear in recurrent pregnancy loss (RPL). The aim of this study is to evaluate the prevalence and clinical significance of anti‐PLG and anti‐t‐PA antibodies in 87 patients with a history of RPL: 54 women with well‐defined PAPS (mean age 32·5 years; range 26–38) and 33 women with unexplained RPL (mean age 30 years; range 24–39). IgG anti‐PLG antibodies were found in 20 and four patients from the group with RPL/PAPS and unexplained RPL, respectively; IgG anti‐t‐PA antibodies were found in 11 and two patients from the above two groups, respectively. IgG anti‐PLG antibodies were associated with the high risk of RPL (OR 7·2, P  = 0·004), especially with RPL/PAPS (OR 11·2, P  < 0·001) evaluated by Fisher's exact test, while IgG anti‐t‐PA were associated with RPL/PAPS (OR 10·0, P  = 0·01) but not with RPL (OR 6·8, P  = 0·06). A significant inhibition of exogenous fibrinolysis was observed by IgG fractions from patients with anti‐PLG or anti‐t‐PA antibodies on microplates and on the human umbilical vein endothelial cells, compared with those from healthy controls. The prevalence of IgG anti‐PLG antibodies was high in RPL patients, especially in RPL/PAPS, while the prevalence of IgG anti‐t‐PA antibodies was high in RPL/PAPS but not in RPL, and some of them might inhibit fibrinolysis in patients.