Immunosuppressive activity of cyclolinopeptide A.

Cyclolinopeptide A (CLA), a cyclic natural nonapeptide isolated in 1959 from linseed oil, was found to possess the immunosuppressive activity of the range comparable to that of cyclosporin A (CS-A). The influence of CLA on the primary and secondary humoral response was determined by the plaque-forming cells test, performed in vitro as well as in vivo. The effect of CLA on the cellular immune response in mice was examined by using (i) the delayed-type hypersensitivity test, (ii) the skin-allograft rejection and (iii) the graft-vs.-host reaction. It was also found that CLA influences human lymphocyte proliferation in vitro and tempers the post-adjuvant polyarthritis in rats and hemolytic anemia of New Zealand Black mice. In all tests performed, the activities of CLA and CS-A were practically the same. Using the plaque-forming cells test and the autologous rosette-forming cells test, we have shown that CLA, like CS-A, inhibits the action of Interleukin-1-alpha and Interleukin-2. Our experiments performed with mice and rats show that intraperitoneal, per os, as well as intravenous application of relatively large doses of CLA does not produce toxic effects. The strong immunosuppressive activity of CLA makes the peptide very interesting from the point of view of its possible utilization in medicine.