The Hsp90 chaperone is up-regulated upon T-lymphocyte activation and necessary for survival of activated cells. (A) Western blot analysis showing Hsp90α and β protein levels of resting and PHA-activated CD4⁺ and CD8⁺ T lymphocytes with vinculin as loading control. (B) Diagrammatic representation of the proportion of apoptotic cells in resting and activated CD4⁺ and CD8⁺ T-cell cultures of 2 donors treated with increasing concentrations of the Hsp90 inhibitor 17-DMAG.