A CLONED LYMPHOID THY1(-SAC CELLS MAINTAINED IN LONG-TERM CELL-CULTURE IN THE ABSENCE OF A THYMIC MICROENVIRONMENT EXPRESSES AN UNUSUAL CELL-SURFACE PHENOTYPE() TUMOR LINE DERIVED FROM MURINE YOLK)

We have previously established conditions under which murine yolk sac cells can be maintained in vitro in the absence of thymus, and we repo rted that a spontaneously transformed Thy1.2+ yolk sac cell line was o btained after long term culture in vitro. We now provide further pheno typic characterization of a clone, YSA1, of this Thy1.2+ cell line sho wing that it expresses Thy1.2, CD3/TCR Vbeta8, IL-2 receptor (IL2R), a nd heat stable antigen (HSAg), but does not express CD4/CD8 or TCR gam madelta. The YSA1 clone is an immature cell as indicated by the expres sion of IL2R and HSAg and by nonproduction of IL-2 upon stimulation by anti-CD3 antibody. The data show that yolk sac stem cells can differe ntiate into CD3/TCR expressing cells in the absence of thymus, but do not progress in vitro paralleling observations made on freshly-isolate d yolk sac stem cells.