Recent data suggest that not only inflammatory status but also humoral immune response to antigens in SCD patients may differ according to treatment. Yazdanbakhsh reported an imbalance between regulatory T cell (Treg) and effector T cell (Teff) in alloimmunized SCD patients with as consequence an increase in antibody production. In a model proposed by the authors, the balance between Treg and Teff is dictated by the monocyte control of cytokines expression. Altered activity of monocyte heme oxidase-1 (HO-1) would be responsible of a decrease in IL-12 and an increase in IL-10 cytokines secretion impacting the Treg/Teff cells ratio and promoting antibody production by B cells.