High-affinity IgE receptor on eosinophils is involved in defence against parasites

Abstract

Parasitic infections are often associated with eosinophilia and high levels of immunoglobulin E (IgE). This observation has led to speculation that eosinophils and IgE may act together in the immune response against parasites. In support of this hypothesis, IgE and eosinophils participate in cytotoxic reactions directed against Schistosoma mansoni larvae in vitro. Furthermore, epidemiological studies have shown an inverse correlation between levels of specific IgE and rates of infection with Schistosoma. The low-affinity IgE receptor (Fc epsilon RII/CD23) was first incriminated in eosinophil activation. The fact that the high-affinity IgE receptor (Fc epsilon RI) is not only expressed on mast cells and basophils but also on Langerhans cells led us to investigate the presence of Fc epsilon RI on eosinophils. Here we show that Fc epsilon RI is expressed on eosinophils from hypereosinophilic patients, is involved in eosinophil degranulation, and participates in eosinophil-mediated cytotoxicity against S. mansoni. Our results indicate that Fc epsilon RI may play a major part in immune defence against parasites.

From allergy to schistosomes: role of Fc receptors and adhesion molecules in eosinophil effector function

“…By flow cytometry, positive staining was detected on 13% to 73% of eosinophils from individual donors. These results indicate that in contrast to mast cells, which constitutively express FcεRI, expression of FcεRI by blood eosinophils was variable among patients (Soussi Gounni et al 1994).…”

“…For this purpose, purified eosinophils, schistosomula targets and IgE antibody-containing immune serum samples were incubated in the presence of a mAb directed against the α chain of FcεRI (mAb 15-1). A dose-dependent inhibition of cytotoxicity was observed with mAb 15-1 but not with the isotype control mAb (Soussi Gounni et al 1994). …”

CD23-Bound IgE Augments and Dominates Recall Responses through Human Naive B Cells

“…Animal models have not been informative in this aspect, primarily due to the differential cellular distribution of IgE receptors (FcεRI and FcεRII/CD23) (28,29). Hypotheses for the role of IgE in helminthiasis have centered on effector functions of FcεRI + myeloid cells that cooperate with IgE to kill parasitic larvae; however, in vivo evidence is lacking in humans (30). Another conundrum in schistosome human immunology is the length of time and exposure required for individuals to demonstrate evidence of resistance (31).…”

IgE‐mediated antigen presentation

“…Clearly, there is a direct connection between IgE titers and the distribution of effector cells which bear high-affinity receptors for IgE (Ec,-RI), such as mast cells and basophils. However, the view that these cells are unique in expressing Fc^Rl cannot be sustained since the recent discovery of FCfRI on normal Langerhans' cells (6,65), on monocytes from atopic patients (36), and on eosinophils in parasitic infections (54). The finding of Fc,-RI in human skin (44) and blood, on cells different from effector cells such as mast cells and basophils, suggests an additional role for IgE in immune responses (38).…”