Heterogeneity of F cells in β-thalassemia.
BACKGROUND
Fetal hemoglobin (HbF), which is largely replaced after birth by the adult Hb, is concentrated in a few "F cells." Their number significantly increases in certain physiologic and clinical situations, including in β-thalassemia (β-thal). Their quantification is used to detect fetal-maternal hemorrhage (FMH), where fetal cells enter the maternal circulation. We were confronted with a pregnant woman with β-thal who was suspected to have FMH. To establish the usefulness of a flow cytometric procedure to differentiate between fetal cells and the maternal F cells, we screened adult β-thal patients.


METHODS
Blood samples were simultaneously stained with fluorescent antibodies to HbF and to carbonic anhydrase (CA) isotype II, which is specific to adult red blood cells (RBCs).


RESULTS
A heterogeneous distribution of RBCs with respect to HbF and CA expression was observed: adult non-F cells (CA+HbF-) and F cells (CA+HbF+/HbF++) as well as F cells with characteristics of fetal cells (CA-HbF++).


CONCLUSIONS
The presence of CA-HbF++ RBCs in nonpregnant women, and even men, with thal indicates that the CA/HbF method is inappropriate for detection of FMH. The coexistence of F cells carrying fetal or adult markers suggests that they originate from two types of stem cell, adult and fetal, lineages. Normally, the fetal lineage is insignificant, but in β-thal, as HbF-containing RBCs have a selective advantage, the "fetal" lineage gains significance.
Department of Hematology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
Eugenia
E
Prus
Eitan
E
Fibach
D000328:Adult; D002256:Carbonic Anhydrases / Q000032:analysis / Q000097:blood / Q000378:metabolism; D004906:Erythrocyte Count; D004912:Erythrocytes / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D005260:Female; D005312:Fetal Blood / Q000737:chemistry / Q000166:cytology / Q000378:metabolism; D005319:Fetal Hemoglobin / Q000032:analysis* / Q000378:metabolism; D005331:Fetomaternal Transfusion / Q000097:blood / Q000175:diagnosis / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D007231:Infant, Newborn; D008297:Male; D011237:Predictive Value of Tests; D011247:Pregnancy; D011250:Pregnancy Complications, Hematologic / Q000097:blood / Q000175:diagnosis; D017086:beta-Thalassemia / Q000097:blood*
D005319:Fetal Hemoglobin; D002256:Carbonic Anhydrases