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Updated: Jul 11, 2025
Contact-Free Co-Culture Model for the Study of Innate Immune Cell Activation During Respiratory Virus Infection
Published on: February 28, 2021
Common Pollen Modulate Immune Responses against Viral-Like Challenges in Airway Coculture Model
Tarleena Tossavainen1, Maria-Viola Martikainen1, Hanna Loukola1
1Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland.
Abstract:
Recent research indicates that exposure to pollen increases the risk and severity of respiratory infections, while studies also suggest that it may possess a protective function. Our aim was to investigate how exposure to common pollen modifies airway cells' responses to viral- or bacterial-like challenges and vice versa. Cocultured A549 and THP-1 cells were exposed to three doses of four different pollens (Alnus glutinosa, Betula pendula, Phleum pratense, or Ambrosia artemisiifolia) and subsequently to Toll-like receptor (TLR) ligands mimicking bacterial and viral challenges (TLR3, TLR4, TLR7/8). The stimulation experiment was replicated in reverse order. Toxicological and immunological end points were analyzed. When cells were primed with pollen, especially with grass (P. pratense) or weed (A. artemisiifolia), the ability of cells to secrete cytokines in response to bacterial- and viral-like exposure was decreased. In contrast, cells primed with viral ligand TLR7/8 showed greater cytokine responses against pollen than cells exposed to ligands or pollen alone. Our results suggest that pollen exposure potentially weakens immune reactions to bacterial- or viral-like challenges by modulating cytokine production. They also indicate that TLR7/8-mediated viral challenges could elicit exaggerated immune responses against pollen. Both mechanisms could contribute to the acceleration and complication of infections during the pollen season.
Insights
Pollen exposure may weaken airway cell responses to bacterial and viral infections, potentially worsening respiratory illnesses. Conversely, viral challenges might heighten immune reactions to pollen, complicating infections during allergy season.
Area of Science:
- Immunology
- Cell Biology
- Environmental Health
Background:
- Pollen exposure's dual role in respiratory infections is debated.
- Understanding pollen's impact on airway cell immunity is crucial for public health.
Purpose of the Study:
- To investigate how common pollens modify airway cell responses to microbial challenges.
- To examine the reciprocal effect of microbial challenges on pollen-induced responses.
Main Methods:
- Co-cultured A549 and THP-1 cells were exposed to various pollens (Alder, Birch, Timothy grass, Ragweed).
- Cells were subsequently challenged with Toll-like receptor (TLR) ligands mimicking bacterial (TLR4) and viral (TLR3, TLR7/8) stimuli.
- Experiments were conducted in both sequential orders to assess priming effects.
Main Results:
- Pollen priming, particularly with grass and weed pollens, reduced cytokine secretion in response to bacterial and viral stimuli.
- Viral ligand (TLR7/8) priming enhanced cytokine responses to pollen compared to pollen or ligand alone.
- Pollen exposure modulated cytokine production, potentially impairing immune defenses.
Conclusions:
- Pollen exposure may suppress immune responses to common respiratory pathogens.
- Viral challenges can lead to exaggerated immune reactions against pollen.
- These interactions may contribute to infection severity and complications during pollen seasons.
