095 | Nanoplastic as modulators of human immune responses: effect on natural killer and T cells

Micro- and nanoplastics are increasingly recognized as emerging environmental contaminants with potential consequences for human health. Although their widespread presence has been documented across multiple environmental matrices, evidence of their occurrence in human biological samples is still limited. The aim of this study was to investigate the interaction between nanoplastics and human peripheral blood mononuclear cells (PBMCs), with a specific focus on T lymphocytes and natural killer (NK) cells, evaluating their immunomodulatory effects through in vitro functional assays. PBMCs from 20 healthy donors were isolated from peripheral blood samples by Ficoll-Paque density gradient centrifugation and cultured for 72 hours. To support NK cell maintenance and survival, 0.5ng/mL IL-15 was added to the culture medium. Cells were exposed to three types of 50 nm nanoplastics (polystyrene, polyethylene, and polypropylene) at a concentration of 2 µg/mL, consistent with previously reported blood levels. Analyses were performed under both unstimulated and PMA/ionomycin stimulation conditions to assess the impact of nanoplastic exposure on immune activation and functional responses. Functional assays were performed to evaluate cell viability, activation, inhibitory receptor expression, and cytokine production. Immune phenotyping and functional readouts were assessed by two 15 colors flow cytometry panels using lineage-specific, activation, and checkpoint markers combined with intracellular cytokine staining. Results showed that nanoplastic exposure was associated with significant differences in activation and inhibitory marker expression in NK, NKT-like, and T cell subsets. Under nanoplastic-stimulated conditions, higher levels of activation markers as CD25, CD69, NKG2D, and NKp46 were observed compared with controls (p ≤ 0.05). This data suggest that nanoplastics may potentiate pro-inflammatory responses in both stimulated and unstimulated conditions. These findings also support the hypothesis that nanoplastics can interact with circulating immune effector cells and alter their functional profile, indicating a potential effect on the immune functions on exposed subjects. Overall, this study provides evidence that nanoplastic exposure may exert immunological effects and underscores the need for deeper investigation into the mechanisms underlying nanoplastic–immune cell interactions and their possible clinical relevance.