The micromechanical properties of leukocytes make a certain contribution to the blood flow velocity in the microcirculatory bed, while the micromechanical properties themselves change under the influence of a complex network of purinergic signals.The aim of the work was to study the micromechanical properties and functional activity of granulocytes in normal conditions and in patients with acute lymphoblastic leukemia when simulating exogenous loading with ATP in vitro.Materials and methods. Leukocytes were isolated from the blood of patients with acute lymphoblastic leukemia and healthy people. Each sample was divided into a test sample and a control sample. In the test samples, the loading with ATP in vitro was simulated. Leukocytes of the control samples were incubated in the culture medium without the addition of ATP. Young’s modulus and adhesion force were measured using an atomic force microscope in the force spectroscopy mode. The cell surface potential was measured in an atomic force microscope in the Kelvin mode. To assess the functional activity of granulocytes, hypoosmotic tests in vitro and determination of migration activity were used.Results. In tests with exogenous ATP, both in samples from healthy people and from patients with acute lymphoblastic leukemia, a decrease in the rigidity and potential of the plasma membrane surface, an increase in the adhesive properties of leukocytes and migration activity were found. At the same time, the responses of granulocytes to the osmotic loading were different: for example, in the group of healthy people, the loading with ATP caused cell contraction and a decrease in the use of the membrane reserve by the cell in a hypotonic environment, and in patients with acute lymphoblastic leukemia, it caused an increase in the volume and more intensive use of the membrane reserve in volume regulation.Conclusion. The revealed effects indicate the leading role of the ATP molecule in the signal transduction mechanisms between blood cells in the microvasculature. The increase in the adhesive properties of the cell surface of granulocytes revealed in the study, in parallel with the increase in their migration activity under the influence of the ATP molecule, can contribute to the development of inflammation in the vessel wall.