2-COLOR IMMUNOCYTOCHEMICAL STAINING OF GAMMA (GAMMA) AND EPSILON (EPSILON) TYPE HEMOGLOBIN IN FETAL RED-CELLS

We have developed a two-colour immunocytochemical staining method for the detection of fetal and embryonic haemoglobin in erythroid cells. T he method was applied to study these haemoglobin types in fetal red ce lls. Specimens from fetal blood (10 weeks), cord blood and fetal liver (14 weeks) as well as chorionic villus samples (10-13 weeks) were sta ined for gamma and epsilon chains using CY3 and FITC labelled antibodi es. Morphometric analysis was applied to determine cell size. Samples from organs involved in early embryonic development contained relative ly large erythroblasts expressing the epsilon globin chain (megaloblas ts); later in gestation the gamma chain was co-expressed by the same c ells which ultimately became smaller and contained HbF (alpha(2)gamma( 2)) only. This phenomenon was confirmed in CVS samples in which all ce ll types were abundantly present. Since fetal erythroblasts are consid ered candidate cells for non-invasive prenatal diagnosis using FISH, w e studied the phenotype of erythroblasts circulating in the maternal b lood. The majority of erythroblasts in maternal blood appeared to be o f the relatively small gamma globin-containing cell type. However, car eful screening of the same maternal blood samples also revealed erythr oblasts expressing epsilon or epsilon and gamma globins simultaneously , although at low frequency. Control specimens from non-pregnant women did not show nucleated red cells expressing either of the haemoglobin types. These observations may contribute to the better recognition of fetal cells in the maternal blood for prenatal diagnosis. (C) 1998 Jo hn Wiley & Sons, Ltd.