Fig. 1. Two-parameter density plots showing the distribution of mononuclear blood cells stained with anti-CD3-eFluor405 antibodies and 4 variants of FITClabeled anti-TRBV9 antibodies (МА-K1, МА-К2, МА-K3, and МА-K4). Every tested anti-TRBV9 antibody was taken at two different concentrations: 3 μg/ml (А) or 200 ng/ml (В) per 10⁶ mononuclear cells. The CD3⁺TRBV9+ population is marked by a small square. The proportion of TRBV9⁺CD3⁺ cells is given relative to all CD3⁺ lymphocytes. С. Staining with different concentrations of the chimeric МА-К2 antibody: 2 ng/ml, 20 ng/ml, 50 ng/ml, 200 ng/ml (top to bottom)

Fig. 2. А. The schematic of the experiment conducted to assess the binding specificity of the chimeric antibody MA-K2 to TCR using cell sorting and the analysis of the TCR repertoire of the sorted cells. Two T-cell populations were obtained: TRBV9⁺ (shown in blue) and TRBV9^- (shown in red) and their TCR repertoires were further analyzed. Results are presented as a proportion of all TCRs identified by sequencing. В. Flow cytometry cytotoxic activity analysis of the chimeric MA-K2 antibody. The panel shows the gated CD45⁺CD3⁺ population; the CD45⁺CD3⁺TRBV9⁺ population is marked by a rectangle. С. Half maximal effective concentration (ЕС₅₀) of MA-K2 estimated by the cytotoxicity test. D. The proportion of dead cells (%TO-Pro3readyflow+) upon addition of 100 ng/ml of MA-K2 to human PBMC and staining with TO-Pro3readyflow. The plots show gated CD4⁺CD3⁺ and CD8⁺CD3⁺ lymphocyte populations. The population of dead cells is marked by a black rectangle