Splenopentin (DAc-SP5)--influence on engraftment and graft-vs-host reaction after non-H-2 bone marrow transplantation in mice

The influence of DAc-SP5 on engraftment and graft-vs-host reaction (GVHR) was studied in different non-H-2 strain combinations. The engraftment was more or less enhanced in every case, whereas the situation in the GVHR was completely different. In one case splenopentin did not influence the course of the GVHR so much, in a second case the symptoms of the GVHR were completely abolished, and in a third case the GVHR was dramatically enhanced up to a great mortality. Therefore, before application of DAc-SP5 to the bone marrow transplantation in humans in order to improve the engraftment, parameters have to be found which allow an exact prediction about the influence of splenopentin on the GVHR in each single case.

Cytofluorometric and cytomorphologic analysis of human bone marrow cells derived from stromal cultures stimulated by granulocyte-macrophage colony-stimulating factor, interferon-gamma and splenopentin pentapeptide

We studied the influence of human recombinant granulocyte-macrophage colony-stimulating factor (hrGM-CSF), human recombinant interferon-gamma (hrIFN-gamma) and splenopentin pentapeptide (Sp-5), either alone or in combination, on the proliferation and differentiation of human bone marrow cells in modified Dexter's cultures. After 10, 14 and 21 days cells were analyzed by classical staining according to Pappenheim and by cytofluorometry with a set of different monoclonal antibodies. IFN-gamma inhibited the proliferation of progenitor cells and provided signals promoting monocytic differentiation, whereas GM-CSF induced the proliferation of blastoid elements which expressed HLA-DR and M2 (VIM-2 monoclonal antibody), but progressively lost surface CD34. Furthermore, an increase of CD15+ cells was also observed. When GM-CSF was tested in combination with IFN-gamma, it abolished the inhibitory effect of IFN-gamma and both cytokines synergized to promote the expression of CD11c, CD14 and M2 surface antigens. Sp-5 alone had only a marginal activity, but it potentiated the effects of GM-CSF. These findings suggest that GM-CSF may induce the transition from stem cells to committed myeloid progenitors. In contrast to IFN-gamma, Sp-5 can serve as an additional proliferative signal with negligible effects on cell maturation.

Splenopentin (DAc-SP-5) accelerates the restoration of myelopoietic and immune systems after sublethal radiation in mice

In 1981 a new splenic hormone was described by Audhya et al. (Biochemistry, 20, 6195-6200, 1981). At first designated as thymopoietin III, the complete amino acid sequence had been described as splenin in 1984. For the pentapeptide corresponding to amino acids 32-36 of splenin was shown to be active in immunological systems. The synthetic pentapeptide splenopentin (DAc-SP-5) and the sequence 32-36 of splenin are identical. In this study the recovery of immunocompetence in mice following sublethal irradiation is shown to be enhanced by DAc-SP-5. The treatment effects of DAc-SP-5 were verified by splenic plaque-forming response to a T-cell dependent antigen and in the hematopoietic colony-forming assay. These effects were associated with an accelerated recovery of leukocyte counts in peripheral blood and spleen without significant changes in the relation between leukocyte and lymphocyte subpopulations. Furthermore, in comparison to control animals DAc-SP-5 treated mice showed in the first weeks postexposure a significantly higher number of bone marrow derived cells as well as granulocyte-macrophage and macrophage colony-forming cells (GM-CFC and M-CFC). Therefore, DAc-SP-5 may be a useful substance for treating secondary forms of bone marrow depression.