Immunosuppressive effects of factor IX products: an in vitro study

The effects of a recombinant factor IX product (BeneFix), and of five plasma-derived factor IX products, AlphaNine, Immunine, Konyne, Mononine and Replinine on in vitro peripheral blood mononuclear cell (PBMC) immune function were compared in a blinded study. We assessed the effects of these products on Con-A-induced lymphocyte proliferation and interleukin-2 and interleukin-10 secretion, expression of lymphocyte activation markers, and nitric oxide secretion by stimulated mouse peritoneal macrophages. At 1 mL-1 for 48 h, Konyne reduced Con-A-induced mitogenesis by 50% (P < 0.05); AlphaNine, Mononine and BeneFix had no effect. At 10 IU mL-1, Con-A-induced mi- togenesis was at control levels with Mononine and BeneFix, but was reduced to <15% (P < 0.05) with each of the other products. IL-2 and IL-10 secretion by Con-A-stimulated lymphocytes was also markedly depressed by all the products tested except Mononine and BeneFix. Dialysis of these products did not substantially affect these results. Flow cytometric analysis of lymphocyte activation markers following Con-A stimulation showed that Konyne also decreased IL-2 receptor alpha and beta chain (CD25 and CD122) induction on PBMC. Konyne also inhibited nitric oxide secretion to levels <18% of controls. These results indicate that certain factor IX products, including some of purported higher purity, substantially depress in vitro immune function. The importance of these findings to in vivo immune function in haemophilia B patients remains to be established.