A431 cells originally normally respond to heat stress. A – A431 cells were heated at 42°C for 40 min and lysates of control and heat-shocked cells were analyzed by Western blot using 2H9 anti-Hsp70 antibody. The amount of Hsp70 production shown on the Western blot was quantified by densitometry and normalized to the total protein loaded into each lane of the gel. B – control and heat-stressed cells were stained with the 2H9 anti-Hsp70 monoclonal antibody. Scale bar indicates 5 μm.