Oral Exposure to Polypropylene Microplastics Exacerbates Cow’s Milk Allergy in a Murine Model by Skewing the DCs/T-Cell Response toward Th2 Polarization

Recent evidence indicates that polypropylene (PP) infant feeding bottles release nano-/micro-plastics (NMPs) during formula preparation; however, their effects on cow's milk allergy (CMA) remain unknown. This study investigated the impact of oral PP exposure on CMA in a murine model. Results showed that PP exposure significantly aggravated allergic symptoms, specific antibody responses, and intestinal barrier dysfunction caused by CMA. Moreover, PP potentiated systemic and local Th2 responses while simultaneously impairing oral tolerance by depleting p-Tregs and Th2-like Tregs. Profiling of DCs revealed that PP suppressed tolerogenic cDC1 subsets while expanding the proallergic cDC2B population and upregulating OX40L expression. An in vitro DCs/T-cell coculture system confirmed that PP enhanced antigen uptake by DCs and shifted naïve T-cell differentiation toward Th2 polarization, eventually aggravating CMA susceptibility. This study highlighted the potential health risk posed by NMPs contamination in food and suggested a possible contribution to the escalating prevalence of CMA in infants.