Relationship between clinical features and binding domains of anti-prothrombin antoantibodies in patients with systemic lupus erythematosus and antiphospholipid syndrome

Akimoto, T Akama, T Kono, I Sumida, T

T. Akimoto et al., Relationship between clinical features and binding domains of anti-prothrombin antoantibodies in patients with systemic lupus erythematosus and antiphospholipid syndrome, LUPUS, 8(9), 1999, pp. 761-766

25

INGLESE

Article

Rheumatology

LUPUS

0961-2033 → ACNP

8

9

1999

761 - 766

ISI

0961-2033(1999)8:9<761:RBCFAB>2.0.ZU;2-X

Autoantibodies against prothrombin, including lupus anticoagulant antibodie s (LAC), have been identified in patients with systemic lupus erythematosus (SLE) and antiphospholipid syndrome (APS). To identify the epitopes of LAC in patients with SLE and APS, we analyzed B cell epitopes of anti-prothrom bin Abs. Prothrombin was purified from fresh plasma samples from healthy su bjects, and fragmented by thrombin. Two fragments (prethrombin-1, 50 kDa, a nd fragment-1, 22 kDa) were separated and used for further experiments. The two fragments were coated on irradiated plate and the binding activities o f sera from 13 patients with anti-prothrombin Abs (SLE, 7; APS, 4; SLE + AP S, 2) were determined by using ELISA. The assay was conducted under the fol lowing conditions: use of irradiated plates, and TBS containing Tween-20. W e detected two types of anti-prothrombin Abs. The first was anti-prethrombi n-1 (n = 5) while the other was Ab against fragment-1 (n = 8). There were n o patients with Abs that showed binding activities to both fragments. A hig her proportion of patients with thrombosis were positive for anti-prethromb in-1 Abs (80%) than for anti-fragment-1 Abs (25%). Two patients with anti-p rethrombin-1 Ab were positive for LAC and negative for anti-cardiolipin-bet a(2) glycoprotein I antibody (aCL-beta(2)GPI). Our results strongly support the notion that both prethrombin-1 and fragment-1 on prothrombin molecule are B cell epitopes.