It is well recognised that haemostasis may be achieved in patients with FVIII inhibitors using FIX concentrates (PTX). However, it has not been possible to correlate the clinical response with enzymicity, FVIII levels and other in vitro results. This is partially due to the presence of variable amounts of inhibitors and stabilizers such as: citrate, heparin, and anti proteases in different preparations. Agarose gel electrophoresis was performed in an attempt to separate these inhibitors so that the various activities may be measured relative to one another. PTX from 4 sources were used in this study,(Kabi Vitrum, Immuno, Oxford and Edinburgh fractionation centres); FVIII was measured by two stage clotting(FVIII:C)and amidolytic (CAM) assays, and its electrophoretic distribution was followed by preincubation with 125I-anti VIII:C (VIII:CAg). Enzymicity was measured with various substrates (S2160, S2222, S2302, S2238, S2288, S2251). All concentrates showed a fast moving peak of FVIII:C and VIII:CAm activity, in amounts in excess of that detected before electrophoresis. This peak correlated well with the distribution of bound radiolabel (VIII:CAg). Preincubation of PTX with FVIII concentrate caused the VIII:CAg peak to migrate more slowly, in its normal α 2 position. FVIII:RAg was present in much lower amounts than FVIII:C. When a twin- peak of VIII:CAm activity was sometimes seen, the slower peak was associated with S2288 activity, which may represent the action of activated factors VII or IX: other substrates showed variable patterns of enzymicity but the strongest activity was with S2160 and S2302 from the well to the β region, and this could be completely inhibited by addition of anti Kallikrein. The presence of an abnormal molecular form of FVIII, and the discrepancy between pre and post electrophoresis FVIII levels, indicate that FVIII could play a major role in the action of PTX. This may involve 1) a complex with phospholipid, FIX and FX making it potentially more effective; 2) enhancement of VIII:C activity in vivo by binding to FVIII:RAg; 3) altered antigenic sites on the FVIII, making it unrecognisable to inhibitor.
Serum monoclonal immunoglobulin bands in undifferentiated lymphomas of Burkitt and non-Burkitt types
