Metal-induced
hypersensitivity is driven by dendritic cells (DCs) that migrate from the site of exposure to the lymph nodes, upregulate costimulatory molecules, and initiate
metal-specific CD4+ T cell responses. Chronic
beryllium disease (CBD), a life-threatening
metal-induced
hypersensitivity, is driven by
beryllium-specific CD4+ Th1 cells that expand in the lung-draining lymph nodes (LDLNs) after
beryllium exposure (sensitization phase) and are recruited back to the lung, where they orchestrate granulomatous
lung disease (elicitation phase). To understand more about how
beryllium exposures impact DC function during sensitization, we examined the early events in the lung and LDLNs after pulmonary exposure to different physiochemical forms of
beryllium. Exposure to soluble or crystalline forms of
beryllium induced alveolar macrophage death/release of IL-1α and
DNA, enhanced migration of CD80hi DCs to the LDLNs, and sensitized
HLA-DP2 transgenic mice after single low-dose exposures, whereas exposures to insoluble particulate forms
beryllium did not. IL-1α and
DNA released by alveolar macrophages upregulated CD80 on immature BMDC via IL-1R1 and TLR9, respectively. Intrapulmonary exposure of mice to IL-1R and TLR9 agonists without
beryllium was sufficient to drive accumulation of CD80hi DCs in the LDLNs, whereas blocking both pathways prevented accumulation of CD80hi DCs in the LDLNs of
beryllium-exposed mice. Thus, in contrast to particulate forms of
beryllium, which are poor sensitizers, soluble or crystalline forms of
beryllium promote death of alveolar macrophages and their release of IL-1α and
DNA, which act as
damage-associated molecular pattern molecules to enhance DC function during
beryllium sensitization.