Growth inhibition induced by bortezomib in T lymphocytes as assessed by MTT. Results are expressed as mean percentage (±SD) of absorbance at 570 nM using a spectrophotometer (100% is considered as the corresponding value of the sample incubated without bortezomib [0 nM]). Significant differences (P < .01) in cell growth were observed between PHA-stimulated T lymphocytes, MLR, and controls for the different concentrations of the drug (n = 11). When T lymphocytes were cultured with irradiated allogeneic dendritic cells (DC), T lymphocytes displayed an intermediate proliferative pattern between PHA-stimulated cultures and MLR (n = 9). Significant differences (P < .01) were observed in terms of percentage of growth inhibition within T lymphocytes stimulated with PHA, MLR, or irradiated DCs depending on the concentration of bortezomib.