LAUSR

e14179 Background: Previously, regression of the developed transplanted tumors under the influence of magnetite nanoparticles (NPs) as monofactor was shown. The purpose of the study was to reveal signs of intercellular interactions in the zone of tumors regressed under the influence of magnetite NPs. Methods: Experiments were carried out on 14 white outbred male rats (180-200 g) with transplanted sarcoma 45 of an initial volume of 0.7-1.3 cm3. After 6 peritumoral injections of magnetite NPs (10 ± 2 nm) in the form of magnetic fluid AM-01 ("AM-Kub", Ekaterinburg) twice a week in a single dose of 17.7 mg/kg, 5 out of 7 rats of the main group demonstrated a regression of the tumor from 1.5-3 cm3 to 0.7 ± 0.2 cm3 (in the control group – 9.7 ± 1.9 cm3, p < 0.01). Ultrathin sections of the tumor tissue of 12 animals (including 7 rats of the main group) were examined in electron microscope JEOL JEM-1011 (Japan). Results: Under effective action of magnetite NPs in tumor tissue, in addition to necrosis, apoptosis and autophagy were marked. In the case of apoptosis, chromatin condensation in compact masses and separation of apoptotic bodies were observed. Significantly more common autophagic cell death was identified by violation of the integrity of the cell membrane and the presence of autophagosomes. Numerous signs of activation of cell-cell interactions with participation of immune cells were observed. Diverse groups of 2-4 contacting cells included macrophages, lymphocytes, plasmocytes, degranulated mast cells, neutrophils in various combinations with distinct signs of the metabolic activity. Invagination of macrophages cytoplasm into the cytoplasm of tumor cells, close adjacency of the cytoplasmic membranes of neutrophils and lymphocytes at considerable length, tight intertwining of mast cell cytoplasmic processes and engulfing of the mast cell granules by macrophages were noted. Conclusions: The results supplement the characteristics of immune processes during the self-dependent antitumor action of magnetite NPs.