Peripheral blood dendritic cells express Fc ε RI as a complex composed of Fc ε RI α- and Fc ε RI γ-chains and can use this receptor for IgE-mediated allergen presentation

Abstract

Originally limited to basophils and mast cells, the spectrum of high affinity IgE receptor (Fc ε RI-bearing cells has expanded recently to include Langerhans cells, dermal dendritic cells (DC), monocytes, and eosinophils. As a result of studies on the distribution, structure, and function of Fc ε RI on APCs, we discovered a minor nonbasophil, nonmonocyte PBMC population that can bind IgE via Fc ε RI. This receptor occurs on the surface of these cells as a multimeric structure containing Fc ε RI α- and Fc ε RI γ-chains but, unlike its counterpart on basophils, lacking Fc ε RI β. Further experiments revealed that these Fc ε RI α γ-expressing cells closely resemble peripheral blood DC by immunophenotype (HLA-DRhigh, HLA-DQhhigh; CD4+, CD11a+, CD32+, CD33+, B7/2 (CD86)+; CD11blow, CD14low, CD40low, CD54low, CD64low) and cell morphology. These features allowed us to isolate Fc ε RI-expressing DC from the peripheral blood and to investigate their immunostimulatory properties. We found Fc ε RI-positive DC to be efficient stimulators of both primary (allogeneic MLR) and Fc ε RI/IgE-dependent, secondary T cell responses at low cell numbers. Thus, Fc ε RI-expressing DC may not only amplify established type I allergic immune reactions but, unlike Fc ε RI-positive semiprofessional APCs, may be able to prime naive T cells to common and/or cryptic epitopes of IgE-reactive Ags.