The immunity in the mammary gland can be, as in other systems, classified in innate or adaptive immunity. The innate immunity is the predominant defense during the initial periods of infection. The non-specifics answers are present or are quickly activated in the infection's site by numerous stimulations, and these answers are not enhanced by repeated exposure to the same agent. The first obstacle to be faced by the agent is the barrier represented by the teat sphincter and the keratin plug. When the pathogenic agent crosses the teat canal and reaches the teat cistern, starts to act the humoral factors and the phagocytic cells starts do act. Among the humoral mediators there are the lactoperoxidase, complement, cytokines, lactoferrin, lysozyme and NAGase. The non-specific cellular defenses are represented by neutrophils, macrophages and natural killer cells. If these mechanisms have been functioning adequately, the majority of pathogens will be eliminated in a short time, before the specific immune system be activated. The fast elimination of the microorganisms will not allow these alterations in the amount or quality of produced milk. The best understanding of the defense mechanisms of the mammary gland and its alterations during the critical periods of infection, is an useful tool in devising and developing methods to control the mastitis, the major illness of dairy ruminants. This paper overviewed the most important aspects of the innate immunity of bovine mammary gland.
bovine mastitis; innate immunity; mammary gland