A new anti-hemoglobin F antibody against synthetic peptides for the detection of F-cell precursors (F-blasts) in bone marrow

To date there are few antibodies available for the detection of fetal hemoglobin (HbF)-containing erythroblasts (F-blasts) in paraffin-embedded hematopoielic tissues. Recently, we developed a new polyclonal antibody specific to F-blasts by immunization of a rabbit with synthetic peptides of human HbF. Specificity and reactivity of the antibody were confirmed by enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry. ELISA confirmed that the antibody showed strong immunoreactivity to fetal hemoglobin but no reaction to adult hemoglobin. The antibody could detect the presence of fetal blood hemolysates (10 μg/mL) at a dilution of 10^-5. According to immunohistochemical analysis, there were strong positive reactions to fetal erythroblasts in the liver and the spleen at 29 weeks of gestation and to erythroblasts from patients with myelodysplastic syndromes and erythroleukemia but no reactions to normal adult erythroblasts in bone marrow. Fetal erythrocytes in fetal blood vessels of placental tissues were strictly distinguished from maternal erythrocytes in the same sections by their positive reactions, indicating the presence of HbF. This new antibody will be a useful tool for studying fetal hemoglobin synthesis and for detecting F-blasts in archival specimens of various hematological diseases.