Neutrophils expressing major histocompatibility complex class II molecules circulate in blood and milk during mastitis and show high microbicidal activity

• DOI: 10.3168/jds.2022-22728
• Publication Date: 2023-04-18T19:31:35Z
• Authors: Marion Rambault; Florence B. Gilbert; Philippe Roussel; Alexia Tessier; Valérie David; Pierre Germon; Nathalie Winter; Aude Remot
• Keywords: [SDV.IMM] Life Sciences [q-bio]/Immunology; Neutrophils; 610; Cattle Diseases; Cell Count; mastitis; bactericidal response; Major Histocompatibility Complex; SF221-250; Mammary Glands, Animal; neutrophils; 616; Animals; Mastitis, Bovine; major histocompatibility complex class II; Inflammation; [SDV.BA.MVSA]Life Sciences [q-bio]/Animal biology/Veterinary medicine and animal Health; [SDV.BA.MVSA] Life Sciences [q-bio]/Animal biology/Veterinary medicine and animal Health; SF250.5-275; 3. Good health; Dairying; Milk; [SDV.IMM]Life Sciences [q-bio]/Immunology; Cattle; Female; Dairy processing. Dairy products

Bovine mastitis is mainly caused by bacterial infection and responsible for important economic losses as well alterations of the health welfare animals. The increase in somatic cell count (SCC) milk during due to influx neutrophils, which have a crucial role elimination pathogens. For long time, these first-line defenders been viewed microbe killers, with limited orchestration immune response. However, their more complex: we recently characterized bovine neutrophil subset expressing major histocompatibility complex class II (MHC-II) molecules (MHC-IIpos), usually distributed on antigen-presenting cells, having regulatory capacities cattle. In this study, our objective was evaluate implication different neutrophils subsets mammary gland immunity clinical subclinical mastitis. Using flow cytometry, analyzed presence MHC-IIpos blood at time points inflammation (n = 10 infected quarters) mastitis, defined bacteria an SCC >150,000 cells/mL 27 quarters). Our results show, first that milk, are heterogeneous population encompass least 2 distinguishable expression MHC-II. without observed higher production reactive oxygen species phagocytosis capacity compared MHC-IIneg counterparts, indicating high bactericidal neutrophils. enriched but not Moreover, positive highly significant correlation between T lymphocytes present experiments involved total 47 cows (40 Holstein 7 Normande cows). To conclude, study opens way discovery new biomarkers inflammation.