The immune system has evolved over millions and millions of years as an extremely potent and efficient defence mechanism directed towards a single goal; to keep us healthy. The primary function of the immune system is to protect the body against infections by pathogenic viruses, bacteria, fungi and parasites. It also plays a key role in preventing and repairing (oxidative) damage caused by stress due to environmental factors such as irradiation, sub-optimal temperatures, (drink) water quality, toxins and human handling. Occasionally, the immune system may overreact or be brought out of balance. Such imbalances can result in immune disorders like low-grade inflammation (e.g arthritis, gingivitis), allergies or other health conditions. The immune system can be suppressed, resulting in reduced overall resistance to (pathogenic) infections. Therefore a properly functioning immune system is essential for good health of all animal species.
Three major principles of immunity are common to all living creatures; recognition, processing and elimination of threats. The immune system needs to recognise the invading danger (by distinguishing between self and non-self), process this information and eliminate the threat. All animals should stay healthy by employing these ‘simple’ principles.
An organism that can cause disease is called a pathogen. The virulence of a pathogen varies greatly and depends on its ability to evade the body’s defences. The body’s defences include physical barriers (e.g. skin, intestinal wall, mucous) that exclude invaders, innate immunity (a-specific) that provides rapid initial protection and adaptive (specific) immunity that provides prolonged effective immunity. A properly functioning immune system can distinguish between pathogens and their own healthy tissue.
Whilst the importance of a well-functioning immune system is evident, multiple examples of sub-optimal immunity are often observed. Immune suppression by, for example, stress, medication or ageing can make animals more susceptible to infectious diseases or other immune-related problems. A proper antioxidant status will support the animal during challenges where oxidative stress is present, for example, the release of reactive oxygen species (ROS) during immunological infections. Imbalances of the immune status can result in allergic reactions, (chronic) inflammations or auto-immune diseases. Optimisation of the immune response can be beneficial in the case of many health issues.
Feed additives can play a role in the support and optimization of the immune status of animals. Feed additives can act as immunomodulators, have anti-inflammatory effects, support the antioxidant status and have a (direct) anti-pathogenic effect. From different angles, feed additives are able to optimize the immune status of production and companion animals, resulting in an improved animal health status.