CLONING OF A NOVEL CELL TYPE FROM HUMAN FETAL LIVER EXPRESSING CYTOPLASMIC CD3-DELTA AND CD3-EPSILON BUT NOT MEMBRANE CD3

Seventeen-week human fetal liver cells cultured with a feeder cell mixture of irradiated PBL, irradiated JY cells (an EBV-transformed B cell line) and PHA contained a subpopulation of CD3- cells in addition to a major population of T cells with the mature phenotype. After 12 days in culture, CD3- CD16- cells were sorted and cloned by limiting dilution. Two representative clones, FL121 and FL125, were expanded and characterized. They shared the phenotype of CD2+CD3-CD4-CD5-CD6+CD16-CD56+. FL121 did not express CD8 whereas FL125 expressed CD8-alpha but not CD8-beta. Both clones were found to express cytoplasmic CD3-delta and CD3-epsilon-Ag while CD3- NK clones isolated from PBL were negative for them. These results indicate that FL121 and FL125 were committed to the T-cell lineage. Southern blot analysis showed that the TCR-beta-genes and the TCR-gamma-genes of these clones were in the germ-line configuration. The establishment of FL121 and FL125 may provide a novel insight into the earliest stage of T-cell development in man.