ИСТИНА

Leukocytes or white blood cells (WBCs) play a key role in the body’s resistance to various types of pathologies. Determination of WBC’s concentration in the blood as well as the ratio between major leukocyte’s subpopulations (neutrophils, eosinophils, basophils, monocytes, lymphocytes) is the gold standard in clinical practice of monitoring immune response. Also, not only WBC’s quantitative composition in blood, but metabolic status of immune cells is significant for diagnostics, as well as an understanding of the processes in which WBCs are involved. Despite the great advances of label-free optical methods, their applicability for assessing WBC’s status is not fully disclosed. In this work we investigated the usability of the endogenous autofluorescence properties (both spectrally and time-resolved) of WBCs for their detection and separation into various subpopulations, as well as for assessing their metabolic status in vitro and in vivo. We observed that autofluorescence features could be used for classification WBC’s subtype. Also, the possibility of label-free monitoring of erythrophagocytosis (a phenomenon in which macrophages phagocytose red blood cells) was studied. It was found that products of erythrophagocytosis have a characteristic intense autofluorescence response shifted to the red and near-infrared part of spectrum. This specific autofluorescence signal can be used for non-invasive diagnosis of internal bleeding, hemorrhagic atherosclerotic plaques, and other processes with active erythrophagocytosis [1, 2]. We believe that results of this study can be implemented into the clinical practice for in vitro tests and for in vivo diagnostics of processes involving white blood cells. [1] Htun, N. M., Chen, Y. C., Lim, B., Schiller, T., Maghzal, G. J., Huang, A. L., ... & Stocker, R. (2017). Near-infrared autofluorescence induced by intraplaque hemorrhage and heme degradation as marker for high-risk atherosclerotic plaques. Nature communications, 8(1), 1-16. [2] Yakimov, B. P., Gogoleva, M. A., Semenov, A. N., Rodionov, S. A., Novoselova, M. V., Gayer, A. V., ... & Drachev, V. P. (2019). Label-free characterization of white blood cells using fluorescence lifetime imaging and flow-cytometry: molecular heterogeneity and erythrophagocytosis. Biomedical optics express, 10(8), 4220-4236.