The production of hypochlorous acid (HOCl) is a characteristic of granulocyte activation, a hallmark of the early phase of innate immune responses. In this study, we show that, in addition to its well-established role as a microbicide, HOCl can act as a natural adjuvant of adaptive immunity. HOCl enhances the T cell responses to the model Ag OVA, facilitating the processing and presentation of this protein via the class II MHC pathway. HOCl modification also enhances cross-presentation of the tumor Ag tyrosinase-related protein 2 via class I MHC. The adjuvant effects of HOCl are independent of TLR signaling. The enhanced presentation of HOCl-modified OVA is mediated via modification of the N-linked carbohydrate side chain rather than formation of protein aldehydes or chloramines. HOCl-modified OVA is taken up more efficiently by APCs and is degraded more efficiently by proteinases. Atomic force microscopy demonstrated that enhanced uptake is mediated via specific receptor binding, one candidate for which is the scavenger receptor lectin-like oxidized low-density lipoprotein receptor, which shows enhanced binding to chlorinated OVA. A function of HOCl is therefore to target glycoprotein Ags to scavenger receptors on the APC surface. This additional mechanism linking innate and adaptive immunity suggests novel strategies to enhance immunity to vaccines.

Dual-mode MRI contrast agents consisting of superparamagnetic iron oxide nanoparticle (SPION) cores and gadolinium ions associated with the ionic chitosan protecting layer were synthesized and studied. Gadolinium ions were introduced into the coating layer via direct complex formation on the nanoparticles surface, covalent attachment or electrostatically driven deposition of the preformed Gd complex. The modified SPIONs having hydrodynamic diameters ca. 100 nm form stable, well-defined dispersions in water and have excellent magnetic properties. Physiochemical properties of those new materials were characterized using e.g., FTIR spectroscopy, dynamic light scattering, X-ray fluorescence, TEM, and vibrating sample magnetometry. They behave as superparamagnetics and shorten both T₁ and T₂ proton relaxation times, thus influencing both r₁ and r₂ relaxivity values that reach 53.7 and 375.5 mM⁻¹ s⁻¹, respectively, at 15 MHz. The obtained materials can be considered as highly effective contrast agents for low-field MRI, particularly useful at permanent magnet-based scanners.