Interferon-sensitized hematopoietic progenitors dynamically alter organismal immunity.

Inflammation has enduring impacts on organismal immunity. However, the precise mechanisms by which tissue-restricted inflammation conditions systemic responses are poorly understood. Here, we leveraged a highly compartmentalized model of skin inflammation and identified a surprising type I interferon (IFN)- mediated activation of hematopoietic stem/progenitor cells (HSPCs) that results in profound changes to systemic host responses. Post-inflamed mice were protected from atherosclerosis and had worse outcomes following influenza virus infection. This IFN-mediated HSPC modulation was dependent on IFNAR signaling and could be recapitulated with the administration of recombinant IFNα. Importantly, the transfer of post-inflamed HSPCs was sufficient to transmit the immune suppression phenotype. IFN modulation of HSPCs was rooted both in long-term changes in chromatin accessibility and the emergence of an IFN- responsive functional state from multiple progenitor populations. Collectively, our data reveal the profound and enduring effect of transient inflammation and more specifically type I IFN signaling and set the stage for a more nuanced understanding of HSPC functional modulation by peripheral immune signals.

Ultralow protein adsorbing coatings from clickable PEG nanogel solutions: benefits of attachment under salt-induced phase separation conditions and comparison with PEG/albumin nanogel coatings.

Clickable nanogel solutions were synthesized by using the copper catalyzed azide/alkyne cycloaddition (CuAAC) to partially polymerize solutions of azide and alkyne functionalized poly(ethylene glycol) (PEG) monomers. Coatings were fabricated using a second click reaction: a UV thiol-yne attachment of the nanogel solutions to mercaptosilanated glass. Because the CuAAC reaction was effectively halted by the addition of a copper-chelator, we were able to prevent bulk gelation and limit the coating thickness to a single monolayer of nanogels in the absence of the solution reaction. This enabled the inclusion of kosmotropic salts, which caused the PEG to phase-separate and nearly double the nanogel packing density, as confirmed by quartz crystal microbalance with dissipation (QCM-D). Protein adsorption was analyzed by single molecule counting with total internal reflection fluorescence (TIRF) microscopy and cell adhesion assays. Coatings formed from the phase-separated clickable nanogel solutions attached with salt adsorbed significantly less fibrinogen than other 100% PEG coatings tested, as well as poly(L-lysine)-g-PEG (PLL-g-PEG) coatings. However, PEG/albumin nanogel coatings still outperformed the best 100% PEG clickable nanogel coatings. Additional surface cross-linking of the clickable nanogel coating in the presence of copper further reduced levels of fibrinogen adsorption closer to those of PEG/albumin nanogel coatings. However, this step negatively impacted long-term resistance to cell adhesion and dramatically altered the morphology of the coating by atomic force microscopy (AFM). The main benefit of the click strategy is that the partially polymerized solutions are stable almost indefinitely, allowing attachment in the phase-separated state without danger of bulk gelation, and thus producing the best performing 100% PEG coating that we have studied to date.

Nanogel surface coatings for improved single-molecule imaging substrates.

Surfaces that resist protein adsorption are important for many bioanalytical applications. Bovine serum albumin (BSA) coatings and multi-arm poly(ethylene glycol) (PEG) coatings display low levels of non-specific protein adsorption and have enabled highly quantitative single-molecule (SM) protein studies. Recently, a method was developed for coating a glass with PEG-BSA nanogels, a promising hybrid of these two low-background coatings. We characterized the nanogel coating to determine its suitability for SM protein experiments. SM adsorption counting revealed that nanogel-coated surfaces exhibit lower protein adsorption than covalently coupled BSA surfaces and monolayers of multi-arm PEG, so this surface displays one of the lowest degrees of protein adsorption yet observed. Additionally, the nanogel coating was resistant to DNA adsorption, underscoring the utility of the coating across a variety of SM experiments. The nanogel coating was found to be compatible with surfactants, whereas the BSA coating was not. Finally, applying the coating to a real-world study, we found that single ligand molecules could be tethered to this surface and detected with high sensitivity and specificity by a digital immunoassay. These results suggest that PEG-BSA nanogel coatings will be highly useful for the SM analysis of proteins.