Słoń Jj

The immunomodulatory activity of tetra- and tripeptides of tuftsin-kentsin group

It was found that tuftsin (Thr-Lys-Pro-Arg) and its tetrapeptide analogues with the same amino acid composition, but different sequences, demonstrate immunosuppressive activity for the humoral, but not (excepting the Thr-Lys-Arg-Pro tetrapeptide) for the cellular, immune response. The splitting of N-terminal residues from these tetrapeptides leads, however, to formation of tripeptides that are active in both humoral and cellular immune response tests. Thus, the biological degradation of peptides of the type investigated can seriously modulate their immunobiological activities. We also found that tetrapeptides Thr-Arg-Lys-Pro and Thr-Lys-Arg-Pro, as well as tripeptides Arg-Lys-Pro and Lys-Arg-Pro, distinctly differ in their immunomodulatory activities, although the structural differences consist in this case only in the displacement of two basic amino acid residues.

Immunoregulatory activity of substance P fragments

The C-terminal SP7-11 pentapeptide (Phe-Phe-Gly-Leu-Met-NH2) was found to suppress in vitro the immune response in a dose of 1-5 micrograms/ml. It produced also a distinct immunosuppression in vivo, by both per os and intraperitoneal, applications. In contrast, the N-terminal SP1-4 fragment (Arg-Pro-Lys-Pro) suppressed the response at a dose of 0.1 microgram/ml, but stimulated it slightly at higher doses (1-5 micrograms/ml). A structural analog of SP1-4 (Gly-Pro-Arg-Pro tetrapeptide) was found to be a strong immunosuppressor at a dose of 5 micrograms/ml, indicating the importance of N-terminal basic residue for the immunoregulatory activity of intact SP.