Generation of Cells with Morphological and Antigenic Properties of Microglia from Cloned EBV-Transformed Lymphoid Progenitor Cells Derived from Human Fetal Liver

Single-cell clones from the Epstein Barr virus transformed lymphoid progenitor-like cell line established from human fetal liver at 8-week gestation, have been derived and characterized. These clones retained immunoglobulin (Ig) and T cell receptor (TCR) genes in their germ line configuration. They expressed HLA-DR and some B lymphoid markers such as CD19, CD20, and in some, the T lymphoid marker, CD2. They did not express surface Igs, CD3, CD4, CD8 or TCRs (α/β, γ/δ). A sensitive RT-PCR assay revealed that they did not express mRNA for a recombination activating gene-1, which is expressed after commitment to lymphoid cells. These results suggest that the established cloned lines are very early lymphoid progenitors that have not yet been committed to lymphoid cell lineage. In one of the lines, FL8.2.1.4, a marked morphological change that resembled microglia was induced when the cells were cultured in the presence of phorbol myristate acetate (PMA). After 72 hr of culture, 5-10% of FL8.2.1.4 cells developed a microglial morphology when stimulated with 10 to 100 ng/ml PMA. The newly generated cells with microglial morphology expressed HLA-DR and stained with Recinus communis agglutinin -1, which has been reported to bind specifically to brain microglia. In contrast, expression of lymphoid markers on cells with microglia-shaped morphology was remarkably diminished by PMA stimulation. Thus, the early lymphoid progenitor cells have the capacity to differentiate into cells with the morphological and antigenic properties of microglia cells. This system might be useful for further understanding of the characteristics and functions of microglia cells distributed in the central nerve system.