<p>The review summarises the basic information on non-specific factors of mammals that potentially have antimicrobial action. A comparison of previously known factors with the latest literature data is carried out. The following peptide and protein factors are considered: lysozymes, transferrins, interferons, interleukin-2, antimicrobial peptides (defensins, cathelicidins, histatins) and protective glycoproteins (mucins, lectins). These major antibacterial factors perform regulatory functions in the immune system, and some are also able to resist viral and fungal infections or oncological pathologies. The study of the internal antibacterial factors of mammals and the mechanisms of their activation is of great importance for the fight against bacterial infections, including antibiotic-resistant ones. This knowledge is necessary for the development of new approaches to the treatment of humans and farm animals.</p> Graphical Abstract <p></p>