SERA FROM HABITUAL ABORTERS INDUCE MONOCYTE PROCOAGULANT ACTIVITY - ALYMPHOCYTE-DEPENDENT EVENT

Placental thrombosis is a prominent feature in patients with unexplain ed recurrent fetal loss. To determine whether induction of monocyte pr ocoagulant activity might be a relevant mechanism for unexplained recu rrent fetal loss, peripheral blood mononuclear cells isolated from nor mal healthy controls were cocultured with (a) sera from normal healthy controls (n = 16), (b) sera from habitual aborters (n = 41), and (c) lipopolysaccharide as a positive control. Sera from three patients wer e fractionated on Sephracryl S-300 and the inducing molecule(s) charac terized. Sera from normal healthy controls failed to induce procoagula nt activity above basal levels of 21 +/- 4.6 mU/10(5) peripheral blood mononuclear cells. Of the sera from 41 habitual aborters examined, 26 (63%) induced procoagulant to a mean value of 410 +/- 48 mU/10(5) per ipheral blood mononuclear cells (P < 0.01). Sera from 15 patients fail ed to augment procoagulant activity. The induction of procoagulant act ivity was maximal after 6 hr of incubation and was lymphocyte dependen t. Fractionation of serum from the three patients on Sephacryl S300 re vealed the procoagulant activity (PCA)-inducing factor(s) to have a mo lecular weight of between 300,000 and 800,000 Da. The serum factor was found to be heat, alkaline, and acid sensitive. Both anti-IgM and ant i-IgA immunoabsorbents reduced the PCA-inducing factor. We conclude th at IgM and IgA from some patients with unexplained recurrent fetal los s are capable of inducing procoagulant activity and could contribute t o the development of placental microthrombi and infarction, prominent features of this syndrome. (C) 1994 Academic Press, Inc.