Amino acid transport in thymic- and spleen-derived lymphocytes.

We have examined the transport of amino acids by the sodium-dependent "A" and "ASC" system in thymic- and splenic-derived lymphocytes from the Long-Evans rat. Lymphocytes derived from the thymus transport amino acids by both the "A" and "ASC" systems, whereas lymphocytes from the spleen transport amino acids by the "ASC" system only. Thymic lymphocytes are capable of establishing a steady state distribution ratio of 7.9 for 2-aminoisobutyric acid, but splenic lymphocytes can attain only 3.5. The steady state distribution ratio of alanine was the same in both cell types. Sodium-independent transport is also different in splenic and thymic lymphocytes. But both cells move amino acids by a Na+-independent system for mediated exchange-diffusion. The studies show that lymphocytes derived from the spleen and thymus transport amino acids differently, and that the "T" lymphocytes from the spleen have membrane transport systems different from "T" lymphocytes from the thymus.