Differential effects of interleukin-3 on fetal and adult erythroid cells in culture: implications for the isolation of fetal cells from maternal blood

Abstract

Fetal clonogenic erythroid cells may be present in maternal blood and serve as a source of fetal DNA for prenatal genetic diagnosis. Proliferating nucleated red cells in cultures from first and second trimester fetal blood contain only fetal haemoglobin (HbF; F+A- cells), whereas nucleated red cells from adult blood contain also adult haemoglobin (HbA; F+A+ or F-A+ cells). Thus, fetal red cells can be identified and flow sorted. However, a few adult cells are also F+A-, which reduces the purity of fetal cell isolation. Culture media optimized for erythropoiesis contain interleukin-3 (IL3). We show here that IL3 strongly stimulates the growth of F+ cells (both F+A- and F+A+) in cultures from adult blood but has only a comparatively small effect on F+A- cells in cultures from fetal blood. This difference is maintained in the unified conditions of co-cultures of adult and fetal cells, so that the purity of fetal cell sorts can be increased by omitting IL3 from the culture medium. We further show that IL3 accelerates the exhaustion of the long-term division potential of adult cells, allowing fetal secondary colonies to be identified by their size following a two-stage culture scheme. Thus, the choice to omit or include IL3 in the growth medium of maternal blood cultures should depend on whether fetal nucleated red cells are to be isolated by flow sorting after one week, or by picking secondary colonies after a later secondary culture stage.