Food-Associated Xenobiotics and Innate Immunity: Molecular and Cellular Effects of Imazalil, TBHQ (Tert-Butylhydroquinone), Carrageenans, and Monosodium Glutamate

Food-associated xenobiotics may influence innate immune responses, but the relevance of experimental findings to human dietary exposure remains uncertain. This narrative review critically examines evidence concerning imazalil, tert-butylhydroquinone (TBHQ), carrageenans, and monosodium glutamate (MSG), representing a post-harvest fungicide, a synthetic antioxidant, a hydrocolloid, and a flavor enhancer, respectively. Experimental findings are compared across cellular and humoral innate immune endpoints, with attention to chemical form, dose, administration route, exposure duration, and the distinction between biomarker changes and adverse functional outcomes. Reported effects involve redox-sensitive signaling, cytokine regulation, macrophage and neutrophil responses, NK-cell activation and effector-associated markers, and intestinal barrier–microbiota interactions. These overlapping processes do not establish equivalent mechanisms or immunotoxic potential. TBHQ has a comparatively well-characterized connection to Nrf2 activation, although Nrf2 dependence has not been established for every reported immune effect. Imazalil evidence is narrower and requires independent replication, whereas findings for carrageenans depend strongly on material characterization and experimental context. MSG findings vary with dose, route, life stage, and metabolic conditions. Moreover, the predominantly preclinical literature includes exposure conditions whose correspondence to human dietary intake is uncertain. Consequently, available evidence supports context-dependent innate immune modulation but does not establish clinically meaningful immune impairment at customary dietary exposure. Further progress requires exposure-informed studies linking molecular and cellular changes to persistent functional effects and adverse outcomes, supported by human-relevant systems and human investigations where feasible. Such evidence would clarify the contribution of innate immune endpoints to food-safety assessment.