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The Platelet/Megakaryocyte Axis is Necessary for Allergic Sensitisation and Inflammatory Responses to House Dust Mite
Anna Chalidou1, Katie-Marie Case1, Carl Hobbs2
1Pulmonary Pharmacology Unit, Institute of Pharmaceutical Science, King's College London, Room 5.43 Franklin Wilkins Building, Waterloo Campus, London, SE9 1NH, UK.
Background:
Evidence demonstrates that megakaryocytes (MKs) possess antigen processing and presentation properties. We investigated whether sensitisation to house dust mite (HDM) extract and the establishment of allergic pulmonary inflammation was dependent on the presence of platelets, and whether the allergic phenotype had an effect on antigen-presenting marker expression on MKs and platelets.
Methods:
Balb/c mice were administered anti-GPIbα antibody or an isotype control during days 0, 2, and 4 to temporarily deplete circulating platelets during initial sensitization to allergen (HDM extract) via an extended intranasal administration on days 0-4, 7-11, and 13. Bronchoalveolar lavage was undertaken, along with blood samples, and lung histology to quantify leukocyte recruitment, Th2 cytokine analysis, and lung platelet deposition. Lung MKs, bone marrow MKs, and circulating platelets were analysed from both allergen-sensitized and non-sensitized mice for the expression of MHC class I, MHC class II, FcεRIα, and CD40.
Results:
Temporary platelet depletion limited to the initial phase of allergen sensitization inhibited the development of the allergic pulmonary phenotype to HDM as demonstrated by reduced eosinophil recruitment, IgE titre, IL-4 and IL-13 expression. Lung-resident MKs demonstrated higher expression of MHC class II and FcεRIα when compared to bone marrow (BM) MKs on establishment of an allergic phenotype, suggesting the administration of HDM specifically affected the immune-phenotype of the lung niche of MKs rather than the bone marrow niche, or systemic effects on circulating platelets. Platelets within the lung were observed to have increased co-localisation frequency with CD11c-positive antigen-presenting cells (APCs), but not CD4-positive T cells, suggesting that platelet activation may occur during the initial steps of allergen sensitisation.
Conclusion:
The platelet/MK axis is a requirement for sensitisation to HDM. An allergic phenotype selectively influences the immune signature of MKs in the lung.
Insights
Platelets and megakaryocytes (MKs) are essential for house dust mite (HDM) sensitization. Allergic reactions alter MK immune markers specifically within the lungs, not systemically.
Area of Science:
- Immunology
- Hematology
Background:
- Megakaryocytes (MKs) have antigen-presenting capabilities.
- Investigated the role of platelets in house dust mite (HDM) sensitization and allergic pulmonary inflammation.
- Examined how allergic phenotype affects antigen-presenting marker expression on MKs and platelets.
Purpose of the Study:
- To determine if platelet presence is necessary for HDM sensitization and allergic lung inflammation.
- To assess if an allergic phenotype impacts antigen-presenting marker expression on MKs and platelets.
Main Methods:
- Temporary platelet depletion using anti-GPIbα antibody in Balb/c mice during HDM sensitization.
- Intranasal HDM administration to induce allergic inflammation.
- Analysis of bronchoalveolar lavage, blood, and lung histology for immune cell recruitment and cytokine expression.
- Flow cytometry analysis of MKs and platelets for MHC class I, MHC class II, FcεRIα, and CD40 expression.
Main Results:
- Platelet depletion during initial sensitization inhibited allergic pulmonary responses to HDM, including reduced eosinophils, IgE, IL-4, and IL-13.
- Lung-resident MKs showed increased MHC class II and FcεRIα expression compared to bone marrow MKs in allergic mice.
- Platelets in the lung co-localized more with antigen-presenting cells (APCs) than T cells, suggesting early activation during sensitization.
Conclusions:
- The platelet-MK axis is crucial for sensitization to HDM.
- Allergic phenotype selectively modifies the immune signature of lung MKs.
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