Stimulation of the recruitment of epidermal Langerhans cells by splenopentin

Identification of delta- and mu-type opioid receptors on human and murine dendritic cells

The purpose of this study was to evaluate mu- and delta-opioid receptors (OR) on human and murine dendritic cells (DC). Expression of mu- and delta-OR mRNA on DC was demonstrated by RT-PCR. The immunocytochemical and Western blot analyses revealed the expression of OR protein in DC. Radioreceptor assay demonstrated the specific saturated temperature-dependent binding of [3H]-labeled opioid ligand on DC and B(max)=2.8+/-0.3 fmol/10(6) cells and K(D)=4.8+/-1.0 nM were calculated by a Scatchard analysis. Finally, OR ligands DADLE and DAGO dose-dependently modulated the capacity of DC to induce T cell proliferation in an MLR assay. Importantly, expression of functional OR on DC was significantly increased upon TNF-alpha-induced DC maturation. Thus, these data suggest a new mechanism of opioid-dependent neuroendocrine immunomodulation.

Thymopentin and splenopentin as immunomodulators. Current status

Splenopentin (SP-5, Arg-Lys-Glu-Val-Tyr) and thymopentin (TP-5, Arg-Lys-Asp-Val-Tyr) are synthetic immunomodulating peptides corresponding to the region 32-34 of a splenic product called splenin (SP) and the thymic hormone thymopoietin (TP), respectively. TP was originally isolated as a 5-kDa (49-amino acids) protein from bovine thymus while studying effects of the thymic extracts on neuromuscular transmission and was subsequently observed to affect T cell differentiation and function. TP I and II are two closely related polypeptides isolated from bovine thymus. A radioimmunoassay for TP revealed a crossreaction with a product found in spleen and lymph node. This product, named splenin, differs from TP only in position 34, aspartic acid for bovine TP and glutamic acid for bovine splenin and it was called TP III as well. Synthetic pentapeptides (TP-5) and (SP-5), reproduce the biological activities of TP and SP, respectively. It is now evident that various forms of TPs were created by proteolytic cleavage of larger proteins during isolation. cDNA clones have been isolated for three alternatively spliced mRNAs that encodes three distinct human T cell TPs. The immunomodulatory properties of TP, SP, TP-5, SP-5 and some of their synthetic analogs reported in the literature have been briefly reviewed.

Stimulation of IL-2 production and CD2R expression by splenopentin analogs

Splenopentin (SP-5), is a pentapeptide corresponding to the amino acid sequence 32-36 (Arg-Lys-Glu-Val-Tyr) of the splenic hormone splenin. Its synthetic analogs: Lys-Lys-Glu-Val-Tyr(1) and D-Lys-Lys-Glu-Val-Tyr (2) have been evaluated for active T-cell rosette (CD2R), total T-cell rosette (CD2), interleukin-2 (IL-2) stimulation and effect on antibody production. SP-5 as well as both the analogs stimulated CD2R. Analogs (1) and (2) were also found to stimulate IL-2 production. These observations suggest that in vitro human NK cell augmentation with analogs (1) and (2) reported earlier may be due to enhanced IL-2 production.

The effect of splenopentin (DA SP-5) on in vitro myelopoiesis and on AZT-induced bone marrow toxicity

Splenopentin (DA SP-5) is a pentapeptide corresponding to the amino acid sequence 32-36 (Arg-Lys-Glu-Val-Tyr) of the splenic hormone splenin. We examined the influence of DA SP-5 on bone marrow progenitor cell (BMC) proliferation. DA SP-5 acts as a co-stimulant for recombinant human granulocyte-macrophage colony-stimulating factor (rHuGM-CSF) in the induction of human BMC derived colony formation in vitro (colony-forming units). When exposed to DA SP-5 and thereafter to AZT and rHuGM-CSF, BMCs show a colony-forming response similar to that after cultivation with the rHuGM-CSF alone. In contrast, when exposed to AZT and rHuGM-CSF (and not preincubated with DA SP-5) the colony formation was reduced. A similar pentapeptide thymopentin (Arg-Lys-Asp-Val-Tyr) did not influence colony formation by human BMCs. We assume that DA SP-5 could support therapeutic effects of rHuGM-CSF.

Role of Langerhans cells and other dendritic cells in viral diseases

Langerhans cells are part of a vast system of potent antigen-presenting cells known under the name of dendritic cells. During the last decade, much has been learned on dendritic cell involvement in the immune response to infectious diseases. This review briefly summarizes our current understanding of the role played by Langerhans cells and other dendritic cells in the pathogenesis of DNA and RNA virus infections. These data may form the basis for the development of innovative approaches in the diagnosis, prevention, and treatment of viral diseases.

Augmentation of human natural killer cells by splenopentin analogs

Splenopentin, Arg-Lys-Glu-Val-Tyr (SP-5) and its synthetic analogs; Arg-D-Lys-Glu-Val-Tyr (pentapeptide 1), Lys-Lys-Glu-Val-Tyr (2), D-Lys-Lys-Glu-Val-Tyr (3), Arg-Lys-Gly-Val-Tyr (4), and Arg-Lys-Gln-Val-Tyr (5) have been examined for augmentation of human natural killer (NK) cell activity and human T-cell transformation response. Pentapeptides 2 and 3 were found to significantly augment the in vitro human NK cell activity. However, none of them had any effect on lymphocyte proliferative responses.