Fig. 6
Inhibition of the mitogenic response of human peripheral blood mononuclear cells (PBMCs) to TSST-1 by MS473. (A) To determine the effective proliferative dose of TSST-1, fresh human PBMCs (~ 106 cells/ml) were incubated with the TSST-1 protein at concentrations of 1, 10, 25, 50, and 100 ng/ml (0.04, 0.4, 1.04, 2.1, and 4.2 nM, respectively) for 48 h at 37 °C, 5% CO2. The cells incubated with PBS served as the control. The proliferation of PBMCs and the formation of cell clumps induced by TSST-1 were investigated using an inverted microscope
(B) To determine the inhibitory activity of MS473 on TSST-1-induced mitogenesis, fresh human PBMCs (~ 106 cells/ml) were incubated simultaneously with the TSST-1 protein (2.1 nM), and the serial dilutions of MS473 or SP220 (0.1–4.7 µM) for 48 and 72 h at 37 °C, 5% CO2. The cells incubated with the TSST-1 protein (2.1 nM) and PBS or PBS alone served as the controls. The MS473 scFv exhibited a significant inhibitory effect (the IC50 value: 1.5 µM) on the proliferation of PBMCs and decreased the number of colony-forming cells. The samples were run in triplicate, and the results are expressed as mean ± standard deviation (SD).