Reactive carbonyls are a major Th2-inducing damage-associated molecular pattern generated by oxidative stress.

Oxidative stress is widespread and entwined with pathological processes, yet its linkage to adaptive immunity remains elusive. Reactive carbonyl (RC) adduction, a common feature of oxidative stress, has been shown to target proteins to the adaptive immune system. Because aldehydes are important mediators of carbonylation, we explored the immunomodulatory properties of model Ags modified by common bioactive aldehyde by-products of oxidative stress: 4-hydroxy-2-nonenal, malondialdehyde, and glycolaldehyde. Ag modification with all three aldehydes resulted in Ag-specific IgG1-dominated responses in adjuvant-free murine immunizations in an RC-dependent manner. The central role of RCs was confirmed, as their reduction into nonreactive groups abrogated all adaptive responses, despite the presence of other well-known aldehyde-driven adducts such as N(ε)-carboxymethyllysine and glycolaldehyde-pyridine. Moreover, Ag-specific Ab responses robustly correlated with the extent of RC adduction, regardless of the means of their generation. T cell responses mirrored the Th2-biased Ab isotypes by Ag-specific splenocyte production of IL-4, IL-5, and IL-13, but not IFN-γ. The RC-induced Th2 response was in sharp contrast to that induced by Th1/Th2 balanced or Th1-biasing adjuvants and was maintained in a range of mouse strains. In vitro studies revealed that RC adduction enhanced Ag presentation with Th2 polarization in the absence of conventional dendritic cell activation. Taken together, these data implicate commonly occurring RC as an important oxidation-derived Th2 immunomodulatory damage-associated molecular pattern with potentially important roles in health and disease.