The function of
IgE class-specific suppressor factor (
IgE-TsF) from T hybridomas was studied by employing
IgE-producing B hybridomas.
IgE-TsF was obtained from
IgE class-specific T hybridomas, which had been established by the fusion of a
phosphorylcholine-conjugated Mycobacterium-primed T cell population with the T
lymphoma cell line BW5147. The absorption experiments showed that
IgE-TsF from T hybridomas was composed of the binding site(s) for
IgE and I region gene products as observed in conventional
IgE-TsF. Incubation of
IgE-producing B hybridomas with
IgE-TsF for 1 hr at 37 degrees C resulted in the reduction of the number of
IgE-secreting cells when assessed by a reverse plaque assay. The proportions of surface
IgE-positive cells were concomitantly reduced. After 24 hr incubation with
IgE-TsF, the number of cytoplasmic
IgE-positive cells was reduced, showing that
IgE synthesis was inhibited by
IgE-TsF.
Antigen-specific
TsF from
phosphorylcholine-specific T hybridomas did not show any inhibitory effect, and
IgE-TsF did not block the antibody production of
IgM-producing B hybridomas. Precapping of
IgE receptors by anti-epsilon antibody or the simultaneous addition of soluble
IgE with
IgE-TsF abrogated the suppressive function, suggesting that
IgE-TsF acted directly on B epsilon cells through binding with
IgE receptors.