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

Abstract

Summary. Factor concentrates have been shown to have a variety of immunomodulatory effects in vitro. The presence of plasma-derived factor VIII (pdFVIII) has been shown to diminish lymphocyte proliferative response to mitogens. Recently, we have shown the presence of transforming growth factor-b (TGF-b) as an immunomodulatory component present in plasma-derived FVIII concentrate. However, the addition of neutralizing antibody to TGF-b did not abrogate the inhibitory effect of pdFVIII on monocyte cytokine production, suggesting the presence of other, as yet undetermined, immunomodulatory agent/s in pdFVIII. To further characterize the immunomodulatory effects of pdFVIII, the in vitro effect of pdFVIII concentrate on proliferation and apoptosis of mitogen-stimulated T cells was studied using whole blood and purified T cells. The presence of pdFVIII increased the apoptosis of phytohaemagglutinn (PHA) -stimulated CD4 and CD8 T-cell subsets as determined by Annexin V binding and DNA fragmentation. T-cell subsets showed a pdFVIII dosedependent inhibition of entry into S-phase and G 1 arrest. Addition of neutralizing anti-TGF-b reduced some of these changes. To determine the physiological relevance of these findings, blood samples from five patients receiving FVIII prophylaxis were similarly studied ex vivo and showed significantly increased apoptosis of T-cell subsets as determined by Annexin V staining. TGF-b has been reported to be a potent inhibitor of T-cell proliferation, arresting the cell cycle in G 1 phase and causing apoptosis. Together, these findings suggest that TGF-b is a significant immunomodulatory component of pdFVIII concentrates.

Recombinant and plasma-derived factor VIII products induce distinct splenic cytokine microenvironments in hemophilia A mice

“…30,31 In this study, we also observed higher levels of splenic CD4 ϩ CD25 ϩ Foxp3 ϩ T regulatory cells in mice that were treated with pdFVIII. There are likely to be several factors that contribute to this finding, including the release of the immunosuppressive cytokine TGF-␤ by the CD4 ϩ T cells in pdFVIIItreated mice.…”

Influence of the type of factor VIII concentrate on the incidence of factor VIII inhibitors in previously untreated patients with severe hemophilia A

“…39 TGF␤ is present in relatively large amounts in FVIII LFB 39 but is not the only immunomodulating cytokine present in plasmaderived concentrates. 40 Regarding von Willebrand factor, this factor indeed has a protective action against inhibitor development, as demonstrated in an animal model. 41 It binds to the C2 domain of FVIII, which is frequently the target of anti-FVIII antibodies 42 and contains the binding site for phospholipids (PLs).…”

Risk of inhibitors in haemophilia and the type of factor replacement

“…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. The same group has recently shown that intermediate-purity pdFVIII can inhibit the upregulation of multiple B-cell cytokine receptors for effective antibody production, whereas rFVIII has no effect under the same experimental conditions [33 ].…”