Effect of A20 expression on complementand heat-mediated necrotic cell death. A20 expression protects ECs from complement- but not heat-mediated necrotic cell death. NI PAECs and PAECs infected with rAdA20 or rAdβ-gal were treated with 10% and 20% human serum (hS) as a source of active complement (panel A) or subjected to heat injury by incubating them at 43° C (panel B), and lactose dehydrogenase (LDH) release was evaluated 2.5 hours and 16 hours later by means of CytoTox 9600 nonradioactive kit. Optical density was measured at 490 nm. PAECs treated with 10% heat-inactivated human serum (HIhS) and left at 37° C served as the control for nonspecific cell death, and PAECs left with growth medium alone served as controls for 100% viability. Data for panel A are expressed as mean ± SD of 7 replicates and are representative of 3 independent experiments, and data for panel B are the mean ± SD of 10 replicates and are representative of 7 independent experiments. Total LDH release (TR) was measured in PAECs treated with 0.1% Triton 100X.