ON THE IMMUNOSTIMULATIVE AND IMMUNOSUPPRESSIVE CONFORMATION OF THYMOPENTIN ANALOGS

A series of structural analogues of lactoferrin immunosuppressive pent apeptide I (Arg-Lys-Pro-Val-Asp) were investigated for their immunomod ulatory activity. The series consisted of the following compounds: Arg -Lys-Pro-Val-D-Asp (II), Arg-Lys-D-Pro-Val-Asp (III), Cys(Acm)-Arg-Lys -Pro-Val-Asp-Cys(Acm) (IV), Cys(Acm)-Arg-Lys-D-Pro-Val-Asp-Cys(Acm) (V ) and two cyclic peptides VI and VII: H-Cys-Arg-Lys-Pro-Val-Asp-Cys-OI I (VI) II-Cys-Arg-Lys-D-Pro-Val-Asp-Cys-OH (VII) We found that all the se compounds demonstrate the immunosuppressive activity of diverse ran ge regarding the both: humoral and cellular immune response. Using the conformation of I resulted from X-ray data as tile model ''immunosupp ressive'' conformation we compared it with the ''immunostimulative'' c onformation proposed for thymopentin (TPS) [1]. The tolerance of the b ioactive conformation of I to the configurational change on tile centr al Pro residue was also investigated.