The thrombotic diathesis associated with the presence of phospholipid antibodies may be due to low levels of free protein S.
OBJECTIVE
To determine if abnormalities in the protein C/protein S anticoagulant system exist in patients with phospholipid antibodies who had the primary clinical complaint of fetal wastage.


METHODS
Eleven patients with fetal wastage and phospholipid antibodies were selected for study. Some patients also gave a history of previous thrombotic events related to oral contraceptives and/or pregnancy, but patients were not selected because of a history of clinical thrombosis. The levels of protein C (chromogenic assay), protein S (both free and bound) (Laurell rocket), and C4b-binding protein (Laurell rocket) were measured, and assays for the presence of antibodies against protein S or protein C were performed.


RESULTS
Seven of the 11 patients were found to have low levels of free protein S. Total protein S and protein C levels were within the normal range in all patients. Antibodies to protein C and protein S were not found in any patient. These findings suggest that free protein S levels may be abnormally low in some patients with phospholipid antibodies.


CONCLUSIONS
Free protein S levels are abnormally low in some patients with phospholipid antibodies, and this abnormality may be a factor contributing to the thrombotic diathesis associated with phospholipid antibodies.
Parke
A L
AL
Department of Medicine, University of Connecticut School of Medicine, Farmington 06030-1310.
Weinstein
R E
RE
Bona
R D
RD
Maier
D B
DB
Walker
F J
FJ
D000026:Abortion, Habitual / Q000097:blood / Q000276:immunology; D001323:Autoantibodies / Q000032:analysis*; D001798:Blood Proteins / Q000032:analysis* / Q000276:immunology; D002308:Cardiolipins / Q000276:immunology; D002352:Carrier Proteins / Q000032:analysis; D015935:Complement C4b / Q000032:analysis; D003169:Complement Inactivator Proteins; D005260:Female; D006023:Glycoproteins / Q000097:blood* / Q000276:immunology; D006801:Humans; D016682:Lupus Coagulation Inhibitor / Q000032:analysis; D010743:Phospholipids / Q000276:immunology*; D011247:Pregnancy; D011486:Protein C / Q000032:analysis / Q000276:immunology; D017293:Protein S; D011951:Receptors, Complement / Q000032:analysis; D013927:Thrombosis / Q000097:blood* / Q000276:immunology
D001323:Autoantibodies; D001798:Blood Proteins; D002308:Cardiolipins; D002352:Carrier Proteins; D003169:Complement Inactivator Proteins; D006023:Glycoproteins; D016682:Lupus Coagulation Inhibitor; D010743:Phospholipids; D011486:Protein C; D017293:Protein S; D011951:Receptors, Complement; D015935:Complement C4b