Quantitative and qualitative changes in the cellular composition after incubation with putrescine and cadaverine are considered. The aim of the study was to study changes in the cytological characteristics of leukocytes after their incubation with cadaverine and putrescine. The number, cell types, sizes, presence of vacuoles and inclusions in peripheral blood leukocytes (n=15) were evaluated after their preincubation with cadaverine (5 and 25 mmol/L) and putrescine (5 and 25 mmol/L) for 72 hours at 37oC. It has been shown that as the concentration of putrescine increases, the total number of leukocytes decreases, while cadaverine dose-dependently increased this indicator. At the same time, after exposure to putrescine, the proportion of large lymphocytes and the number of vacuoles in the cytoplasm increased. Cadaverine at a concentration of 25 mmol/L significantly reduced the number of cells with signs of cytolysis. Thus, in the course of the conducted studies, it was found that cadaverine and putrescine, produced mainly by prokaryotic cells, affect both the number and cytological characteristics of immunocompetent cells.