The immunomodulating properties of HEMA is mediated via formation of the NALP3 inflammasome

In Sweden as well as in many other countries most materials currently used for dental restorations contain acrylate and methacrylate monomers (1). As a consequence of increased use of resin-based compounds, there has been an increase in reported cases of irritant and allergic contact dermatitis mainly among dental professionals (2-5). The most common agent causing dermatitis among dental professionals is the acrylate monomer, 2-hydroxyethyl methacrylate (HEMA). Individuals in a dental clinic are, not just exposed to HEMA monomers by skin contact, but they are also exposed to HEMA monomers in the air (5). We have in previous studies shown that HEMA has adjuvant properties. Mice immunized with ovalbumin (OVA) in a solution containing HEMA developed higher anti-OVA IgG1 activity than mice immunized with OVA in a solution without HEMA (6). Mice injected with HEMA-conjugated mouse serum albumin (MSA) produced IgG and IgE autoantibodies (7), and the effect of HEMA on anti-MSA IgG and IgE autoantibody production was dependent on the degree of conjugation of HEMA to MSA. We have also shown that animals immunized with OVA + HEMA have a higher anti-OVA IgE response, which is of special interest with regards to allergy (6). Another finding is that the effect of HEMA is dependent on the buffer used as solvent i.e dissolving HEMA in 100 mM sodium bicarbonate buffer (NaHCO3) results in a stronger anti-OVA IgE response than if HEMA is dissolved in 25 mM NaHCO3 buffer(6). Toll-like receptors (TLRs) are important components of the innate immune system and belongs to the pattern recognition receptors (PRRs. There are 11 different types of TLRs and each one recognizes a specific type of pathogen-associated molecular patterns (PAMPs). TLR4 at the cell surface of monocytes/macrophages recognize lipopolysaccharides (LPS)(8).