It happened to you while repairing the garden fence: you rammed a splinter into your finger. Now the wound turns red, swells and it starts to hurt – first signs of inflammation. Generally speaking, inflammation is a reaction of the body – or more precisely the immune system – to an irritant. The first part of our mini-series tells you what happens when an inflammation occurs in the human and animal body.
Immunity is the body’s natural defense system against various infectious diseases. The factors which trigger immunity include previous infection, immunization, and various external stimuli. The physiologic function of the immune system is to prevent infections and to eradicate established infections. Therefore, the immune system has to differentiate between body’s own (intrinsic) molecules and from foreign (extrinsic) molecules before triggering its responses to invading pathogens. Once, a pathogen entered the body, inflammatory processes initiate the inactivation and elimination of the exogenous antigen.
By definition: an inflammation is
a complex reaction of the innate immune system in vascularized tissues, that involves accumulation and activation of leukocytes and plasma proteins at the site of infection, toxin exposure or cell injury. Inflammation is initiated by changes in blood vessels that promote leukocyte recruitment. Local adaptive immune responses can promote inflammation. While inflammation serves as protective function in controlling infections and promoting tissue repair, it can also cause tissue damage and diseases.
Doubtlessly, this contradiction represents one of the most interesting aspects of biological functions: An inflammation is part of the internal defense mechanisms, but when getting “out of control”, it will cause more harm to the own organism than it helps him. Depending on the organism and the affected tissue even minor inflammation processes can have tremendous consequences: Although an inflammation of the gastro-intestinal tract of livestock animals does not result in a full-blown clinical syndrome, it may lead to a severe performance depression and thus cause economic loss.
In the following, a simplified glance at general processes of inflammation is given:
After an initial drop in blood circulation of the affected region, accompanied by enhanced vessel permeability due to histamine, prostaglandins or serotonin, the blood flow will be increased for several minutes, which causes the typical red and hot appearance of the tissue. In this early stage of immune response, monocytes enter the affected tissues and produce a strong inflammatory reaction, expressing chemokines and cytokines to recruit granulocytes, lymphocytes and further macrophages at the site of infection to enhance phagocytotic activity.
During the inflammation, the transcription factor nuclear factor kappa B (NF-kB) plays a very important role, since its expression, activation and translocation from plasma to nucleus induces the synthesis of above mentioned pro-inflammatory proteins or enzymes involved in the inflammation, apoptosis or cell proliferation. This leads to the assumption, that substances, which down-regulate the expression of NF-kB or stop its translocation, reduce the concentration of pro-inflammatory factors and thus diminish inflammation-related performance depression.