Seasonal allergen exposure recalls IgE+ plasmablasts to reload allergic effector cells

Seasonal allergen exposure boosts the production of Immunoglobulin E (IgE) antibodies, leading to allergic diseases affecting more than 30% of the population. However, the cellular mechanisms and pathological consequences of secondary IgE production in humans remain unclear. Here, we demonstrate that IgE⁺ plasmablasts serve as the dominant cellular source responsible for the seasonal amplification of IgE. During birch pollen season, allergen exposure selectively boosts IgE production targeting pre-established conformational epitopes of the major allergen Bet v 1, with no synchronous increase in Bet v 1-specific IgG. Crucially, this plasmablast-derived IgE re-establishes allergen-specific effector cell activation that declines in absence of allergen exposure. Our findings uncover a key role of IgE⁺ plasmablasts in the rapid recall of allergic responses and highlight their potential as a therapeutic target for allergy.