The expression of
Fc receptors specific for
IgE (Fc epsilon R) and those for
IgG (Fc gamma R) on murine
IgE-specific suppressor T hybridomas was studied. While parental T
lymphoma cells (BW5147) failed to bind
IgE-sensitized red cells (mIgE-TNP-
ORBC), the majority of T hybridoma cell lines having
IgE-specific suppressor activity contained rosette-forming cells (RFC) binding mIgE-TNP-
ORBC (2 to 13% of the total cells). The expression of Fc epsilon R was poor (2% or less) in T hybridoma cell lines without
IgE-specific suppressor activity. In addition to Fc epsilon R,
IgE-specific suppressor T hybridomas also expressed Fc gamma R as detected by
ORBC sensitized with
IgG antibodies (EAox gamma).
beta-Interferon (IFN) (1,000 to 2,000 U/ml) augmented the expression of Fc gamma R, but not of Fc epsilon R. On the other hand, preculture of the cells with 40 micrograms of mIgE per ml enhanced the expression of Fc epsilon R without augmenting Fc gamma R expression.
IgE-specific suppressor activity in the culture supernatants of T hybridomas was also augmented by preculture with mIgE. However, a dissociation between the expression of Fc epsilon R and
IgE-suppressor activity was observed. In some of the subclones, mIgE augmented the suppressor activity without inducing the expression of Fc epsilon R. Furthermore, when treated with 5 micrograms of
melittin, a
phospholipase A2 activator, per ml,
IgE-specific suppressor activity of the hybridomas was completely abrogated, whereas
IgE-induced expression of Fc epsilon R was enhanced by
melittin.