118 Murine Expression of Humanized Toll-Like Receptor 4 Augments Local and Systemic Immune Responses Following Oropharyngeal Aspiration of Nickel Oxide Nanoparticles

Abstract

Abstract It has been demonstrated that murine expression of humanized Toll-like receptor-4 (hTLR-4) confers enhanced immunological responsivity to nickel in the skin; however, it remains unclear if hTLR-4 expression also augments nickel-induced immune responses in the lung. hTLR-4 positive/negative mice of both sexes were exposed to vehicle control (dispersion media) or nickel oxide nanoparticles (NiONP; 48 nm; 2.5, 5, or 20 µg) by oropharyngeal aspiration. Mice were euthanized 1, 7, 14, or 28 days post-exposure. Bronchoalveolar lavage (BAL) was performed, blood was collected, and the lung-associated lymph nodes (LALN) and spleen were harvested for phenotypic analysis. By 7d, total BAL cells, lung LDH, and circulating leukocyte number were all significantly elevated in both female/male hTLR-4 positive mice compared to same-sex hTLR-4 negative mice—effects which normalized by 14d. Dose-responsive increases in LALN size were observed in all NiONP-exposed animals by 14d, but no significant differences were observed between hTLR-4 positive/negative animals. The cellular composition of the LALN and spleen, however, was significantly altered at this timepoint between hTLR-4 positive/negative mice of both sexes. In general, hTLR-4 positive mice exhibited selective increases in proportionality and activation status of CD4+ T-cells and B-cells within both tissues. This alteration remained significant at 28d in female mice only. Collectively, these findings suggest that hTLR-4 expression confers significant alterations in early immune responses to NiONP in the lung and associated lymphoid tissues—effects which may render the hTLR-4 mouse model a more translationally-relevant approach for studying respiratory nickel allergy in vivo.