Lf. Santamaria et al., ANTIGEN FOCUSING BY SPECIFIC MONOMERIC IMMUNOGLOBULIN-E BOUND TO CD23ON EPSTEIN-BARR VIRUS-TRANSFORMED B-CELLS, Human immunology, 37(1), 1993, pp. 23-30
Monomeric IgE bound to the low-affinity receptor for IgE (FcERII-CD23)
on EBV-transformed human B cells selectively enhances binding of anti
gen and therefore presentation to specific T-cell clones. To demonstra
te the role of monomeric IgE in antigen focusing, we have made use of
a system consisting of human T-cell clones specific for Der-P1 (major
allergen of the Dermathophagoides pteronyssinus), Der-P1 coupled to NI
P (Der-P1-NIP), and the commercially available chimeric (human-murine)
monoclonal IgE antibodies with specificity for the hapten NIP. We hav
e found that monomeric IgE binds to CD23 and remains detectable on the
surface of the B cells for a period of at least 16 hours at 37-degree
s-C. Pulsing of these IgE-anti-NIP (1 mug/ml) treated B cells for 1 ho
ur at 37-degrees-C with low amounts (10 ng/ml) of Der-P1-NIP antigen a
llows the B cells to stimulate Der-P1-specific T cells. Even with IgE
concentrations as low as 20 ng/ml, which were not detectable by immuno
fluorescence, we were able to induce a significant T-cell response. Fu
rthermore, ongoing specific T-cell-B-cell interactions were not inhibi
ted by the presence of high concentrations of nonspecific IgE molecule
s (incubated with up to 25 mu/ml) on the surface of the B cells. Our d
ata confirm the hypothesis that IgE, bound by either CD23 or the high-
affinity receptor for IgE, potentiates the immune response. Therefore,
IgE may be seen as the fourth general mechanism for antigen capture b
y (nonspecific) antigen-presenting cells.