Elimination of erroneous results related to bovine mononuclear cell immunophenotyping by antibodies binding to Fc receptors

Direct labeling of milk cells without centrifugation for counting total and differential somatic cells using flow cytometry

Somatic cell count (SCC) in milk is an essential indicator for defining and managing udder health. However, analyzing differential SCC (dSCC) can be helpful in determining the type or evolution stage of mastitis. A high abundance of polymorphonuclear cells (PMN) is associated with acute mastitis; however, the status of a chronic disease is less well characterized. A method capable of analyzing SCC and dSCC can prove to be a helpful tool for monitoring the status of evolution of mastitis disease in a better way. Therefore, a new direct-flow cytometry method was developed to count and differentiate somatic cells in milk without the steps of centrifugation or washing, avoiding variabilities that occur due to enrichment or loss of specific cell types. In this new method, SCC is analyzed using the method of DNA staining with Hoechst stain, whereas dSCC are analyzed using specific antibodies targeting 2 main cell types associated with mastitis: PMN cells and antigen-presenting cells, which are associated with innate and adaptive immunity. Equivalent SCC values were obtained between the new method and the routine ISO 13366-2 method in a comparison of 240 raw milk samples. Furthermore, dSCC results were confirmed by microscopy after May-Gründwald-Giemsa staining in 165 quarter milk samples from healthy and diseased cows. The method was verified with fluorescence microscopy on the 2 targeted cell types and in raw milk samples. The newly developed method is independent of any instrument and can be further designed to differentiate other cell types and animal species by selecting appropriate antibodies.

A polymorphic CD4 epitope related to increased susceptibility to Babesia bovis in Canchim calves

Different allelic forms of bovine CD4 were previously described in cattle and were also observed in Canchim calves examined in the present experiment. However, the functional relevance of these different CD4 phenotypes has not yet been investigated. CD4 + T helper cells are known to play a central role in immune control against Babesia bovis infection. Thus, our study aimed to compare the profiles of immune cells, specific antibody titers and blood infection levels measured by qPCR (quantitative polymerase chain reaction) in calves naturally infected with B. bovis, phenotyped as CD4- (absence of anti-CD4 staining), CD4 + (intermediate staining) or CD4 ++ (high staining). The CD4 mRNA precursor was also measured in these animals. Calves with the CD4- phenotype showed higher amounts of B. bovis DNA in blood samples, compared to the other CD4 phenotypes. It was also observed that these calves with higher levels of infection had lower amounts of natural killer cells and higher expression of the CD4 gene, which can be interpreted as a compensation for the failure of the altered CD4 receptor to recognize relevant B. bovis epitopes.