9 páginasThe major histocompatibility class II complex (MHC-II) play an important effector role for 7 the adaptive immune response against extracellular pathogens. One of the most popular 8 advances for understanding the antigen presentation biological issues is based on the study 9 of the immunopeptidomes, characterizing the peptide repertoire for different the major 10 histocompatibility complex (MHC) allelic variants expressed by professional antigen 11 presenting cells such as macrophages and dendritic cells, allowing the identification of 12 vaccine candidates or therapeutic targets. The present study aimed to evaluate the expression 13 of the MHC-II molecules in bovine mononuclear phagocytic cells infected with two clinical 14 relevant bacteria, determining the best treatment conditions for further studies. We found the 15 differential expression of CD14+ and CD19- on these populations considering different 16 maturation conditions. Interestingly, the phagocytosis and MCH-II expression presented an 17 inverse behavior, obtaining the highest phagocytosis percentages from 2 to 8 hours after 18 infection and the maximum MCH-II expression levels in cells with more than 24 hours of 19 maturation, reducing their phagocytic activity, thus considering a multiplicity of infection MOI) of 1:40 (**P <0.01). Based on this observations, we established the optimal culture 21 conditions for future biological studies in novel areas such as immunopeptidomics.Incluye bibliografía