Factor VIII concentrate inhibits T helper type 2 cytokine productionin vitro: relevance to inhibitor antibody formation

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Abstract
Inhibitor antibody formation in patients with haemophilia receiving factor VIII (FVIII) concentrate is a serious problem. T helper type 2 (Th2) cytokines are necessary for antibody production by B cells and have been shown to be produced predominantly by CD30+/CD45RO+/CD3+ cells. We have previously shown that the Th2 cytokine, interleukin (IL)‐6, is inhibited but IL‐10 is upregulated, in the presence of plasma‐derived FVIII (pdFVIII). To clarify further the overall effect of FVIII on Th2 cytokine production, the percentage of T cells expressing the CD30+/CD45RO+/CD3+ Th2 phenotype was studied over 72 h and the production of the Th2 cytokines, IL‐4 and IL‐5, determined at 24 h in the presence of FVIII following whole‐blood stimulation using multiparameter flow cytometry. The production of IL‐4 and IL‐5 by T cells was significantly inhibited in the presence of pdFVIII. The percentage of CD30+/CD45RO+/CD3+ increased with stimulation of whole blood cultures over 72 h but was significantly inhibited by the presence of pdFVIII or TGF‐β at 72 h. The combined inhibitory effect of prednisolone (a commonly used immunosuppressive agent used to treat patients with inhibitors) with pdFVIII on T‐cell CD30+/CD45RO+ upregulation, was additive. There was no significant alteration in Th2 cytokine production or phenotype noted in the presence of recombinant FVIII (rFVIII) concentrate. Neutralizing antibody to TGF‐β significantly abrogated the inhibitory effects of pdFVIII on Th2 upregulation, indicating TGF‐β to be a major inhibitory component of pdFVIII on Th2 cytokine production. We now provide evidence that pdFVIII, by inhibiting Th2 cytokine production, may result in decreased antibody formation and may be more appropriate than rFVIII at reducing inhibitor formation. A clinical study needs to be undertaken to determine the significance of these in vitro findings.