Consequently, the FVIII-specific CD4+ T cell hybridoma library can only cover a proportion of the FVIII T-cell epitopes found in the total population of patients with severe hemophilia A. However, the particular haplotype HLA-DRB1*1501 was reported to be associated with an increased risk for patients with severe hemophilia A to develop FVIII inhibitors following FVIII replacement therapies (40–42). Here, CD4 is linked to hemophilia A.