Establishment and characterization of a new leukaemic T‐cell line (Peer) with an unusual phenotype

We report the isolation and establishment in continuous culture of a human lymphoid cell line (Peer) from a case of T‐leukemia. The Peer cell line lacks some typical cell‐surface properties of T cells, namely sheep erythrocyte rosette formation and reactivity with two anti‐T‐cell sera, but has focal acid phosphatase and does express two other T‐cell antigens, one defined by a monoclonal antibody, the other related to a T‐cell subset (TH2). The cells are negative for B‐cell markers (Smlg or cytoplasmic μ Fcγ and C3 receptors, mouse erythrocyte rosettes) and EBV (EBNA). In addition, the Peer cell does not possess the typical phenotypic markers of “non‐B, non‐T” leukemia: cALL and la‐like antigens, and the cytoplasmic hexosaminidase isoenzyme I, but is positive for terminal deoxynucleotidyl transferase by enzymatic and immunofluorescent criteria. The cell line requires exogenous L‐asparagine for adequate growth in culture, a property known to be characteristic of certain T cells but not of B cells. The Peer cell line appears to have a maturation arrest at a developmental stage intermediate between the cortical thymocyte and a mature T‐cell subset and to have lost some T‐cell differentiation features.