**5. Conclusions**

As a result of studies to clarify the relationship between the structure and spatial organization (stereochemistry), on the one hand, and the biological properties of analogs 2-5A, on the other one, it was convincingly shown that by changing the structure and/or stereochemistry of their molecules, it is possible to achieve either strengthening of known or giving new properties. The different functional groups of each individual 2-5A nucleotide fragment make a highly specific contribution to the binding and activation of RNase L, as well as to hydrolytic stability.

The use of conformationally rigid 3′-fluorodeoxyanalogs 2-5A and core trimer 2-5A on the example of human NK lymphocytes and mouse macrophages of the P388D1 line allows us to evaluate the influence of structural and stereochemical factors on the cells of the immune system. *Ribo*-fluorodeoxyanalogs 2-5A had a more significant activating effect on human NK lymphocytes and phagocytic activity than *xylo*-analogs or a natural mediator, which is probably due to the closer conformational similarity of *ribo*-fluorodeoxyanalogs with a natural oligomer than with isomeric *xylo*-analogs.

Analogs 2-5A, (2′,5′)A2ARA, and (2′,5′)A2ALA are undoubtedly of considerable interest for transplantology as drugs that prevent kidney rejection, ensure the normal functioning of the transplanted kidney and at the same time do not increase the level of T-helper and T-killer cells in experimental animals in postoperative period.

Undoubtedly, the search for approaches to the directed regulation of the natural protective function of the body with the help of analogs of the core trimer 2-5A can lead to the detection of compounds with high therapeutic potential.
