The present study investigates the effects of
pemphigus IgG and
complement upon cell viability and/or membrane integrity using
trypan blue exclusion,
ethidium bromide (EB) staining, and
fluorescein diacetate (FDA) conversion by living cells. Forty-eight-hour cultivated epidermal monolayers of neonatal BALB/c mice were incubated in media containing 1 mg/ml purified
pemphigus IgG for 48 h in either the presence or absence of
complement (absorbed AB sera). Adherent and detached cells were examined by both phase and fluorescence microscopy. Results from
trypan blue exclusion showed that
pemphigus IgG plus
complement produced a modest decrease in exclusion of the
dye compared to
pemphigus IgG without
complement. When FDA/EB comparisons were made, however, the differences were more substantial. When
complement plus
pemphigus IgG was added to cultures, the number of FDA-positive adherent cells decreased significantly and the number of EB-positive detached cells increased significantly. The effects of
complement were inhibited by the use of heat-inactivated AB sera or by C1q depletion of AB sera. No significant effect on the cells was observed in the presence or absence of
complement when
pemphigus F(ab')2 fragments or when normal
IgG was used.
Plasminogen depletion of the
complement source did not interfere with
complement and
pemphigus IgG effects as judged by the FDA/EB assay. These studies suggest that
pemphigus antibody in the presence of
complement alters cell membrane integrity and supports the contention that
complement may play a significant role in the mechanism of
acantholysis.