A shift towards a T cell cytokine deficiency along with an anti-inflammatory/regulatory microenvironment may enable the synthesis of anti-FVIII inhibitors in haemophilia a patients

Abstract

Despite the clinical relevance of anti-factor VIII (FVIII) antibodies (anti-FVIII inhibitors) impairing haemostatic activity of haemophilia A (HA) patients, the immunological mechanisms underlying their production are unknown. Aiming to understand more clearly the immune response in patients with [HAα-FVIII(+)] and without [HAα-FVIII(-)] anti-FVIII inhibitors, we have characterized the cytokine pattern of peripheral blood leucocytes, using an in vitro stimulation of whole blood samples with plasma-derived (pFVIII) or recombinant FVIII (rFVIII). The results highlighted decreased levels of tumour necrosis factor (TNF)-α + neutrophils with higher interleukin (IL)-5/TNF-α ratio in HAα-FVIII(+). All HA samples displayed decreased levels of IL-10 + monocytes when compared to the blood donor (BD) samples. HAα-FVIII(+) showed lower levels of TNF-α + monocytes and increased IL-10/TNF-a ratio. Analysis of adaptive immunity revealed increased levels of interferon (IFN)-γ +, TNF-α + and IL-4 + T-cells, from both CD4 + and CD8 + T cells, in HAα-FVIII(-) when compared to BD. Moreover, increased frequency of IL-10 + B cells and higher levels of α-FVIII IgG1 were observed in HAa-FVIII(Basal levels of cytokine + B-cells, similar to BD, and higher levels of a-FVIII IgG4 are major features in HAα-FVIII(+). The global cytokine profile demonstrated a major anti-inflammatory/regulatory pattern in HAα-FVIII(+), confirmed by the in vitro stimuli with pFVIII or rFVIII. The polarized anti-inflammatory/regulatory immune response in HAα-FVIII(+) and the mixed pattern with a bias towards an inflammatory cytokine profile, modulated by IL-4 in HAα-FVIII(-), may be the key element to drive the development of distinct subclasses of anti-FVIII antibodies. These finding have implications for the design of safe and effective therapeutic protocols to control inhibitors synthesis in HA patients. © 2010 The Authors. Clinical and Experimental Immunology © 2010 British Society for Immunology.