Expression of anti-inflammatory markers IL-2, IL-10, TGF-β1, βDEF-2, βDEF-3 and Cathelicidin LL37 in dairy cattle milk with different health status of the udder

Great economic losses to the dairy industry are associated with bovine mastitis, which results in poor milk quality and high treatment costs. Anti-inflammatory proteins play an important role in the suppression of the immune response against invading pathogenic microorganisms and are therefore being studied for possible use in the early diagnosis of mastitis. In our study, we used milk samples from 15 cows of Holstein Friesian breed with different health status (5 healthy, 5 subclinical, and 5 clinical animals), and tested them using immunohistochemical (IHC) analysis to evaluate the presence of IL-2, IL-10, TGF-β1, βDEF-2, DEF-3, and Cathelicidin LL37 proteins. The calculation of positively and negatively stained cells for each biomarker was performed using the semiquantitative counting method. We found the presence of all factors with the exception of Cathelicidin LL37, which was almost absent in milk samples of all animal groups. The significant decrease of IL-10, β-def2, and β-def3 expression levels within the 3 days of sampling, found in the milk of animals with sub- and clinical mastitis, indicates the loss of antiinflammatory protection of the affected cow’s udder. In contrast, the stable increase of IL-2 and TGF-β1 positive cells observed in the milk of mastitis-affected cows, and the similar expression of these factors in the milk of healthy animals, indicate the possible lack of involvement of these cytokines at an early stage of udder inflammation.