Chronic allergen exposure drives accumulation of long-lived IgE plasma cells in the bone marrow, giving rise to serological memory.

Immunoglobulin E (IgE) plays an important role in allergic diseases. Nevertheless, the source of IgE serological memory remains controversial. We reexamined the mechanism of serological memory in allergy using a dual reporter system to track IgE(+) plasma cells in mice. Short-term allergen exposure resulted in the generation of IgE(+) plasma cells that resided mainly in secondary lymphoid organs and produced IgE that was unable to degranulate mast cells. In contrast, chronic allergen exposure led to the generation of long-lived IgE(+) plasma cells that were primarily derived from sequential class switching of IgG1, accumulated in the bone marrow, and produced IgE capable of inducing anaphylaxis. IgE(+) plasma cells were found in the bone marrow of human allergic, but not nonallergic donors, and allergen-specific IgE produced by these cells was able to induce mast cell degranulation when transferred to mice. These data demonstrate that long-lived IgE(+) bone marrow plasma cells arise during chronic allergen exposure and establish serological memory in both mice and humans.