CELLS OF THE IMMUNE SYSTEM. OMICS TECHNOLOGIES Flow Cytometry Gating Flow cytometry gating is the selection and analysis of cell subpopulations of interest in multicolor flow cytometry. Typically, the first step of gating includes sorting cells by fluorochrome-targeted CD45 and lymphocytes in forwarding and orthogonal scattered light. Next, a proportion of distinct T-cell subsets is measured since each of them is targeted by a specific fluorochrome. In the course of immune responses, T cells acquire a new phenotype and cytokine profile that can be defined using the following markers: CD45 is Leukocyte Common Antigen; CD27 represents a cell adhesion molecule related to the TNF receptor superfamily, which is responsible for the survival of activated T cells or their apoptosis; CD28 is a costimulatory molecule is adaptive T-cell immune responses; CD62L is a cell adhesion molecule related to the selectin family that plays a role in the first stage, "rolling" action of leukocute transmigration through endothelial cells; CCR7 is a chemokine receptor for chemokines CCL19 (ELC) and CCL21 (SLC) that promote T-cell migration to secondary lymphoid organs; and Cytokines secreted by T cells.секретируемые клетками. Marker Naïve T cells Effector T cells Memory T cells TCM TEM  CD45 (isoforms)  CD45RA+,  CD45RO-  CD45RA+,  CD45RO-  CD45RA-,  CD45RO+  CD45RA-,  CD45RO+  CD27, CD28    CD27+, CD28+  CD27-, CD28-  CD27+, CD28+  CD27+, CD28+  (there are different  expression types)  CD62L  CD62L+  CD62L-  CD62L+  CD62L-  CCR7  CCR7+  CCR7+  CCR7+  CCR7-  Cytokines  IL-2  IFN-γ, TNF-β  IL-2  IFN-γ, TNF-β Researchers sometimes get different data concerning the phenotype of T-cell subsets. In addition, new information is gradually accumulated on the heterogeneity of T-cell subpopulations. The Author wishes to express his gratitude to the information, which was accessible in the course of the webinar on December 7, 2021 (Institute of Experimental Medicine Immunology Dept, Saint Petersburg, and I.P.Pavlov First Saint Petersburg State Medical University Immunology Dept). ©V.V.Klimov