TGF‐β is not the principal immunosuppressive component in coagulation factor concentrates

Abstract

Summary. Coagulation factor concentrates are known to inhibit a variety of immune reactions when assessed in vitro. This study assessed the immunomodulatory activity of a wide range of coagulation factor concentrates by measuring their inhibition of PHA-stimulated lymphocyte proliferation and reduction in IL-2 secretion. The hypothesis that TGF-b is responsible for most of these effects was tested by measuring biologically active TGF-b and immunoreactive TGF-b1 in the concentrates and comparing the levels recorded with immunosuppressive activity. In addition, the coagulation factors were compared directly with a standard preparation of TGF-b in a TGF-b-speci®c bioassay and in lymphocyte proliferation assays. Although there was a broad correlation between levels of total or active TGF-b and immunosuppressive activity across all of the coagulation factors tested, individual data sets showed clear discrepancies. Implying that TGF-b probably serves as a surrogate marker for other immunomodulatory contaminants and that neither TGF-b nor any other single substance could account for all of the immunosuppressive activity observed. Furthermore, there was a difference of more than 100-fold in the relative potencies of coagulation factors and pure TGF-b, when compared in immunosuppression assays, indicating that the different assays did not measure the same substance. Whereas anti-TGF-b antibody almost completely blocked the activity of coagulation factor concentrates (TGF-bspeci®c bioassay) and abrogated the effect of authentic TGF-b (immunosuppression assays) at high concentrations it achieved <50% reversal of the immunosuppressive effects of coagulation factors in immunosuppression assays. These ®ndings indicated that TGF-b accounted for only a minor proportion of the immunosuppressive activity in most coagulation factor concentrates.

Immune tolerance induction with a high purity von Willebrand factor/VIII complex concentrate in haemophilia A patients with inhibitors at high risk of a poor response

“…Moreover, a role of the immunomodulating impurities in the relative success of the study product cannot be definitely excluded. In effect, the plasmaderived clotting factor concentratesÕ content of soluble human leukocyte antigen system (HLA) class I antigens, soluble Fas-ligand and transforming growth factor b 1 have a measurable in vitro immunosuppressive activity as showed by Ghio et al [24], confirming previous findings [25,[30][31][32][33][34][35][36][37]. Nevertheless, Ghio et al [24], who assayed the concentrations of these molecules in clotting factor concentrates, showed that the product used in this study have no immunoglobulin, fibrinogen and fibronectin, and a very low concentration of these other immunosuppressive molecules, comparable with monoclonally purified plasma-derived FVIII products.…”

Risk of inhibitors in haemophilia and the type of factor replacement

“…Lastly, rFVIII may contain a fraction of FVIII molecules which are unable to associate with VWF [30]. Other explanations rely on certain copurified plasma proteins such as transforming growth factor b (TGFb), a potent immune suppressor cytokine that has been detected in nonimmunopurified pdFVIII concentrates but not in rFVIII [31]. It has been suggested [32] that TGFb1 is a major component of the antiproliferative and apoptosis-promoting effects of intermediate-purity pdFVIII on T lymphocytes.…”

Effect of intermediate‐purity factor VIII (FVIII) concentrate on lymphocyte proliferation and apoptosis: transforming growth factor‐β is a significant immunomodulatory component of FVIII

“…However, the addition of neutralizing antibody to TGF‐β did not abrogate the inhibitory effect of pdFVIII on monocyte or natural killer (NK)‐cell cytokine production suggesting that other, as yet undetermined, immunomodulatory agent/s are present in pdFVIII. Another recent report suggests that TGF‐β is not the principal immunosuppressive component in factor concentrates (Pearson et al , 1999).…”