Decreased L-system for amino acid transport in chronic lymphocytic leukemic lymphocytes.

We have defined the kinetic parameters of the L-system of amino acid transport in chronic leukemia of B-lymphocytes (B-cell CLL) and have compared them to those of normal blood lymphocytes, tonsillar lymphocytes, a normal B-lymphocytic cell line (RPMI 1788), and chronic leukemia of T-lymphocytes. The L-system was judged by its affinity for and maximal transport velocity of BCH, a synthetic amino acid whose uptake is virtually limited to the L-system. The L-system of B-cell CLL lymphocytes functioned at less than 15% the rate of the other lymphocyte types, and the substrate affinity of the L-system was lower than that of the other lymphocyte types studied. Thus, the L-system of amino acid transport, a hallmark of normal T- and B-lymphocytes, is vestigial in B-cell CLL. This key functional membrane defect is more closely related to the neoplastic nature of CLL-cells than to their B-lymphocyte phenotype.