The immunosuppressive mini-domain of human lactoferrin.

Abstract

It has been found that the disulphide-bridged 231-245 pentadecapeptide loop of the lactoferrin (LF) N-lobe contains a region of immunosuppressive activity. The activity resides within a thymopentin-like sequence (Arg-Lys-Pro-Val-Asp) of the loop. Peptides related to the 575-589 loop of the LF C-lobe differ in their immunomodulatory activity from those related to the 231-245 loop. We ascribe this difference to the replacement of the Asp residue in the 231-245 loop by Thr in the 575-589 loop. Two other fragments of LF which were studied, 27-34 and 309-315, do not manifest any activity in the DTH test (cellular immune response), but, on testing in vivo, stimulate the humoral immune response. The 27-34 fragment is related to the bactericidal and immunostimulative region of LF identified by Bellamy et al. [1]. Our results show that the LF molecule contains, not only the known immunostimulating mini-domain, but also a region endowed with immunosuppressive activity.