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

Inhibitor antibody formation in patients with haemophilia receiving factor VIII (FVIII) concentrate is a serious problem. T helper type 2 (Th2) cytoki nes are necessary for antibody production by B cells and have been shown to be produced predominantly by CD30(+)/CD45RO(+)/CD3(+) cells. We have previ ously shown that the Th2 cytokine, interleukin (IL)-6, is inhibited but IL- 10 is upregulated, in the presence of plasma-derived FVIII (pdFVIII). To cl arify further the overall effect of FVIII on Th2 cytokine production, the p ercentage 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 stimul ation using multiparameter flow cytometry. The production of IL-4 and IL-5 by T cells was significantly inhibited in the presence of pdFVIII. The perc entage of CD30(+)/CD45RO(+)/CD3(+) increased with stimulation of whole bloo d cultures over 72 h but was significantly inhibited by the presence of pdF VIII or TGF-beta at 72 h. The combined inhibitory effect of prednisolone (a commonly used immunosuppressive agent used to treat patients with inhibito rs) with pdFVIII on T-cell CD30(+)/CD45RO(+) upregulation, was additive. Th ere was no significant alteration in Th2 cytokine production or phenotype n oted in the presence of recombinant FVIII (rFVIII) concentrate. Neutralizin g antibody to TGF-beta significantly abrogated the inhibitory effects of pd FVIII on Th2 upregulation, indicating TGF-beta to be a major inhibitory com ponent of pdFVIII on Th2 cytokine production. We now provide evidence that pdFVIII, by inhibiting Th2 cytokine production, may result in decreased ant ibody formation and may be more appropriate than rFVIII at reducing inhibit or formation. A clinical study needs to be undertaken to determine the sign ificance of these in vitro findings.