MyD88 Dependence of Beryllium-Induced Dendritic Cell Trafficking and CD4(+) T Cell Priming

Beryllium exposure results in beryllium hypersensitivity in a subset of exposed individuals, leading to granulomatous inflammation and fibrosis in the lung. In addition to its antigenic properties, beryllium has potent adjuvant activity that contributes to sensitization via unknown pathways. Here, we show that beryllium induces cellular death and release of IL-1α and DNA into the lung. Release of IL-1α was inflammasome-independent and required for beryllium-induced neutrophil recruitment into the lung. Beryllium enhanced classical dendritic cell (cDC) migration from the lung to draining LNs in an IL-1R-independent manner, and the accumulation of activated cDCs in the LN was associated with increased priming of CD4(+) T cells. DC migration was reduced in TLR9KO mice; however, cDCs in the LNs of TLR9-deficient mice were highly activated, suggesting a role for more than one innate receptor in the effects on DCs. The adjuvant effects of beryllium on CD4(+) T cell priming were similar in WT, IL-1R, caspase-1, TLR2, TLR4, TLR7, and TLR9 deficient mice. In contrast, DC migration, activation and the adjuvant effects of beryllium were significantly reduced in MyD88KO mice. Collectively, these data suggest that beryllium exposure results in the release of DAMPs that engage MyD88-dependent receptors to enhance pulmonary DC function.