Interferon-Gamma (IFN-γ) Secretion Defect in Peripheral Blood Mononuclear Cells (PBMCs) from Severe Hemophilia A (HA) Patients Prior to Therapeutic Exposure To Factor VIII (FVIII) Concentrates.

The recent availability of highly purified recombinant coagulation factor concentrates to treat hemorrhages in hemophilic patients is thought to circumvent perturbations in immune function by preventing chronic intravenous exposure to multiple foreign protein antigens. We previously reported a PHA-induced IFN-γ secretion defect in severe hemophilia A patients who had been exposed exclusively to highly purified coagulation factor VIII concentrates. We now report the results of cytokine secretion in response to PHA in cultured PBMCs from severe hemophilia A patients never exposed to FVIII concentrates. PBMCs were isolated from whole blood from three severe HA patients, 3 age-matched normal boys, 3 boys with severe hemophilia B and an adult control. Cells were stained with PKH26 (Sigma), a fluorescent dye with aliphatic tails that intercalate into membrane lipids; cells were than washed and cultured in complete media in wells of microtiter plates with and without PHA. Cells were harvested at 5 days and proliferation detected by loss of membrane PKH26 staining detected by flow cytometry. Cytokines secreted into the supernatants of 48 hour and 5 day cultures were measured by ELISA assays (BD Pharmingen). PBMCs from severe HA patients proliferated normally in response to PHA but failed to secrete IFN-γ when compared to normal boys and boys with severe HB:

PBMC Proliferation and Secretion of IFN-γ in Response to PHA

The severe HA patients did not have improvement in INF-γ secretion following therapeutic exposure to FVIII concentrates. Addition of physiologic concentrations of FVIII or FIX to cultures with or without PHA did not alter the results of proliferation or cytokine secretion regardless of the inhibitor history of the patients. (1 HA and 1 HB patient developed high responder inhibitors.) Secretion of IL-4, IL-5 and IL-10 were moderately decreased in some HA patients as well. In summary, we have confirmed an INF-γ secretion defect in PBMCs from patients with HA in spite of normal proliferation in response to PHA. The defect is not present in HB or normal age-matched control subjects and is not corrected by addition of FVIII to cultures. We conclude that the defect is not due to exposure to intravenous foreign antigens. The precise clinical significance and any possible relation to the higher risk of inhibitor development in HA will require further investigation.

PBMC Proliferation and Secretion of IFN-γ in Response to PHA