The Immune System – The Body’s Intelligent Control Centre
The immune system protects the body from pathogens and malignant transformation of the body’s own cells, thereby functioning as a natural defense shield for the body. Ideally, lifelong immunity develops because the immune system triggers the appropriate immune response when the body is attacked by pathogens or cancer cells.
Many different organs and cell systems are involved in the immune system.
Immune System Function
The immune system is made up of two subsystems, a nonspecific and a specific component, with different defense mechanisms. They interact in intricate ways to do their job.
Nonspecific Defense (Innate Immune System)
Aging or diseased cells and many common pathogens can be eliminated on first contact by the nonspecific defense system. This is why it is also known as the innate defense system.
The nonspecific immune defense prevents pathogens from entering the body. It therefore also includes the hydrolipid film covering the skin’s surface, the acid pH in the stomach or secretions on the mucous membranes.
The nonspecific immune defense works with cellular and noncellular (so-called humoral) mechanisms:
- Cellular factors: These mechanisms use certain white blood cells that can kill, ingest and digest pathogens or malignant cells, so-called phagocytes, but also scavenger cells and natural killer cells.
- Humoral factors: The nonspecific immune defense also uses substances with an antimicrobial effect that are dissolved in body fluids. These include the enzyme lysozyme, which is found in many body secretions such as tears and saliva and attacks the cell wall of many bacteria. Also part of the nonspecific immune system is what is known as the complement system, an enzyme system formed in the liver that destroys cells that are foreign to the body. In addition, immune hormones like interferons, which can act against viruses, support the nonspecific humoral immune defense.
Specific Defense (Acquired Immune Defense)
The organism only learns specific immune defense over the course of life by direct exposure to a specific pathogen, which is also why it is called acquired immune defense. It consists of a specific immune response tailored to the invader and is activated as soon as the invader has overcome the nonspecific defenses. Playing an important role here are certain groups of white blood cells such as the B cells. They produce large amounts of antibodies. These substances are highly specialized and recognize only certain structures on the surface of invaders.
The antibodies fit infectious pathogens like a key in a keyhole. The next time this harmful pathogen attacks, the key inserts itself in the keyhole and initiates its destruction. Memory B cells are able to form the same antibodies even years later and respond then very quickly. The function of the T lymphocytes is to distinguish between the body’s own and foreign structures. These cells can also develop into memory T cells that recognize the invader again even years later and trigger an immune response. These mechanisms are the basis of immunity.
Role of the Immune System in Infections
The immune system is the body’s primary defense against infectious pathogens. If there is no infection, there is no need to give antibiotics. Even if an infection develops and antibiotics have to be administered, an intact immune system is essential for their efficacy. Antibiotics cannot fight an infection successfully alone.
They always need the help of the cellular and humoral immune response. Gradual impairment in this immune response due to stress, in newborns, during and after virus infections, and in older animals has a major impact on the course of infection and reduces the effectiveness of antibiotics. A delayed and reduced immune response is a (contributing) factor in a reduced effect of antibiotics and promotes development of antibiotic resistance because pathogens have more time to deal with the antibiotic.
Immune System and Antibiotic Resistance
It is known that successful treatment of infected stock with antibiotics does not completely eliminate the pathogen. Here, too, the immune system plays an important role. It normally controls the residual pathogens very effectively. If, however, the immune response of the animals is inadequate, a new outbreak of the pathogen can create a vicious circle.
Resistance and residues have long been problems arising from massive use of antibiotics in farm animals that can no longer be ignored. It is therefore absolutely necessary to develop in the future immunological control strategies that prevent and thereby help to eliminate or at least significantly reduce the use of antibiotics.