Previous studies have shown that sera of patients with severe atopic dermatitis (AD)
contain IgE specific for self-proteins, supporting the hypothesis of autoreactivity
as a pathogenic factor in AD. In this study, we screened a large panel of AD patients
(n=192) by western blotting (WB) for IgE reactivity not only against the human epithelial
cell line A431 but also against primary keratinocytes (KCs). To investigate autoantigenic
cell structures in detail, normal human skin and primary KCs were incubated with sera
from both WB-reactive patients and, for control purposes, healthy individuals, and
analyzed by immunohistology, confocal laser microscopy, and flow cytometry. Our analysis
revealed that 28% of AD patients, but not healthy individuals, display serum IgE autoreactivity
by WB analysis. The individual IgE reaction patterns of the sera pointed to the existence
of unique as well as common specificities against epidermal or A431-derived proteins.
Immunostainings identified cytoplasmic and, occasionally, also cell membrane-associated
moieties as targets for autoreactive IgE antibodies. Interestingly, in certain autoreactive
patients, the surface-staining pattern was accentuated at cellular contact sites.
We conclude that IgE autoreactivity is common, particularly among severe AD patients,
and that non-transformed primary cells are needed for characterization of the entire
spectrum of IgE-defined autoantigens.