Microplastics (MP) are the subject of intensive medical research, but little is yet known about their effects on the immune system. A study led by the Medical University of Vienna now shows that tiny particles of polyethylene terephthalate (PET) remain in the lungs of mice, can exacerbate respiratory tract inflammation and alter the immune responses associated with allergies. The findings were published in the "Journal of Hazardous Materials Advances" and once again highlight the health implications of the increasing environmental burden posed by microplastics.

As part of the study, the research team led by Michelle Epstein (Department of Dermatology, Experimental Allergy Laboratory, MedUni Vienna) investigated the effects of PET particles of varying sizes and dosage forms in a mouse model. PET (polyethylene terephthalate) is one of the most widely used plastics worldwide and is used, among other things, in packaging, drinks bottles, textiles and medical materials.

Following a single administration of medium-sized PET microplastics via the respiratory tract, the researchers found that the particles remained detectable in the lungs for at least 14 days. During this period, an inflammatory response occurred, characterised by increased migration of lymphocytes and eosinophils – immune cells typically involved in allergic reactions. When the administration of PET-MPs was combined with ragweed pollen, a common respiratory allergen, respiratory inflammation was exacerbated under certain conditions. In further experiments, in which PET-MPs were introduced via the abdominal cavity in combination with other allergens, an altered systemic immune response was observed: the PET-MPs exacerbated the inflammation and influenced the antibody response against the allergen.

Active influence on immune responses
"Our study shows that PET microplastics do not simply remain in the body, but actively influence immune responses involved in the development and exacerbation of allergic reactions and inflammation," explains study lead Michelle Epstein. The researchers emphasise, however, that the results were obtained in mouse models and cannot be directly extrapolated to real-world exposure conditions in humans. "Nevertheless, they provide important insights into the potential immunological effects of microplastics, which once again highlight the health relevance of this environmental burden and must be investigated in further studies," says Epstein.