Native defense mechanisms are those that are always active and do not require previous exposure to protect the animal from infection. They can be activated within seconds to minutes after microbial invasion. The major native defense mechanisms includephagocytic cells (neutrophils and macrophages), the complement system, natural killer cells, antimicrobial peptides, and production of native defense cytokines by sentinel cells. Various stressors tend to reduce the efficacy of the native defense mechanisms leading to increased susceptibility to infection. The activity of all of these native defense mechanisms is enhanced if the animal has developed acquired immunity (antibody and T cell-mediated immunity) to a specific pathogen. Since this series of presentations focuses on the immunologic basis for vaccine safety and efficacy, the only aspect of native immunity to be discussed in detail will be the role of sentinel cells in early detection of microbial invasion, activation of native defense mechanisms and induction of acquired immunity.
展开▼
