Lupus anticoagulant-like activity observed in a dimeric lambda protein produced by myeloma cells

We report here a lupus anticoagulant (LA)-like activity observed ina 45-yea r-old man with Bence-Jones protein (BJP) lambda -type multiple myeloma. Thi s patient showed no clinical symptoms of thrombosis or bleeding diathesis, Laboratory examination on admission showed mild anemia. prolongation of act ivated partial thromboplastin time (APTT) (APTT, 56.2 seconds; control. 29. 1 seconds), normal prothrombin time, normal thrombin time, and massive prot einuria (2.3 g/d). The mix test with normal plasma showed the presence of c irculating anticoagulant. Based on the assumption that the lambda -type BJP may have been responsible for the prolongation of APTT. we purified the BJ P from the patient's urine using column works. Sodium dodecyl sulfate-polya crylamide gel electrophoresis and immunoblotting showed that the purified p rotein was a 48-kd homodimer of immunoglobulin lambda -chains. Addition of the purified dimeric lambda -type BJP to the normal plasma prolonged both A PTT and dilute Russell's viper venom time (DRVVT) in a dose-dependent manne r. and the negatively charged phospholipid-dependent prothrombinase activit y was significantly inhibited in the presence of this protein. Furthermore, both the prolongation of DRVVT and the inhibition of the prothrombinase ac tivity were almost completely abrogated under the condition of high ionic s trength. These findings collectively suggest that the dimeric lambda -type BJP showed LA-like activity via the mechanism of ionic charge. Int J Hemato l. 2001;73:526-531. (C) 2001 The Japanese Society of Hematology.