The nonapeptide leucinostatin A acts as a weak ionophore and as an immunosuppressant on T lymphocytes.

Earlier studies have disclosed that leucinostatin A, a hydrophobic nonapeptide antibiotic, assumes an alpha-helical secondary structure in nonpolar environments. The present report demonstrates that the peptide acts as a weak ionophore facilitating the transport of mono-and divalent cations through the plasma membrane of T lymphocytes and through artificial membranes. Leucinostatin A does not change the thymidine uptake of both resting mouse thymocytes and peripheral blood lymphocytes but dose-dependently prevents the activation of T lymphocytes by tetradecanoyl-phorbol-acetate and by anti-T cell receptor antibody.