Abstract
DBA/2 mice which are neonatally infected with Rauscher helper virus (R‐MuLV) develop predominantly lymphatic leukemias. From one of these lymphatic leukemias we established a permanent cell line which we named RLD (Rauscher Lymphoid DBA/2). Phenotyping of this cell line with a panel of monoclonal antibodies directed to cell‐surface determinants shows that RLD cells have T‐cell characteristics: they bind monoclonal antibodies directed to the antigens Thy‐1, T‐200 and Lyt‐1; they do not react with anti‐Lyt‐2 antibodies, nor do they react with antibodies directed to determinants on B cells or myelomonocytic cells. RLD cells show a high activity of the nuclear enzyme terminal deoxyribonucleotidyl transferase (TdT). RLD cells are able to differentiate after in vitro stimulation with 1% DMSO or with 30 nM tetra‐decanoylphorbol‐1.3‐acetate (TPA). This differentiation process is reflected by (I) changes in the 2D gel electro‐phoresis pattern of metabolically labelled proteins, (2) a decrease in TdT activity and (3) changes in the expression of cell‐surface markers. Flow cytometric analysis of stimulated RLD cells shows a strong increase in the Lyt‐1 expression. Together these data indicate that RLD cells are immature T lymphocytes which upon appropriate stimulation differentiate along the line of T helper cells.