FcεRI–FcγRII Coaggregation inhibits IL-16 production from human langerhans-like dendritic cells

Langerhans-like dendritic cells (LLDC) express the high-affinity IgE receptor FcεRI form that lacks the β-chain, and may play an important role in allergic inflammation via production of IL-16. Secretion of mediators by human mast cells and basophils is mediated through FcεRI and is decreased by coaggregating these receptors to the low-affinity IgG receptor, FcγRII. We used a recently described human Ig fusion protein (GE2), which is composed of key portions of the human γ1 and the human ε heavy chains, to investigate its ability to inhibit IL-16 production from FcεRI-positive Langerhans-like dendritic cells through coaggregation of FcγRII and FcεRI. Unstimulated LLDC-derived from CD14-positive monocytes from atopic donors were shown to express FcγRII, an ITIM-containing receptor, but not FcεRI or FcγRIII which are activating (ITAM) receptors. When passively sensitized with antigen-specific, human IgE and then challenged with antigen, LLDC were stimulated to produce IL-16. However, when FcεRI and FcγRII were coaggregated with GE2, IL-16 production was significantly inhibited. Exposure of LLDCs to GE2 alone did not induce IL-16 production. Our results further extend our studies demonstrating the ability of GE2 to inhibit FcεRI-mediated responses through coaggregation with FcγRIIB and at the same time show that human LDCC can be modulated in a fashion similar to mast cells and basophils.