Probiotics and Immunity

Have you ever wondered how the body can tell the difference between a "good bacteria" and a "bad bacteria?" When a pathogen enters the body, several immune specific responses are triggered. These responses are the result of the pathogens interaction with the epithelial and immune cells of the gastrointestinal tract. When a pathogen or "bad germ" enters the body, the body's natural immune system sends out killer cells to destroy the pathogen. The question is, how can the body tell the difference between "bad" bacteria and "good" bacteria?

The epithelia cells in the gastrointestinal tract express both surface and intracellular receptors that can identify bacterial and viral components. This ability allows them to respond by producing substances that will help to maintain or strengthen the epithelial cells. This ability to discriminate between different microbial species is due to the activation of Toll-like receptors (TLR) in the epithelial cells. These receptors are capable of activating various responses of the cell to potential danger. These receptors are normally inhibited and are only expressed during inflammation.

The adaptor protein (MyD88) is necessary for TLR signaling. If there is a deficiency in this protein, TLR signaling may become disrupted causing the epithelial cells to fail to produce the factors important to promoting healing and to prevent epithelial cell apoptosis.

"Good" bacteria, like probiotics, are defined as living microoganisms or microbial mixtures that are administered to "beneficially affect the host animal by improving its microbial balance." Probiotics are helpful suppressing undesirable bacteria and promoting the abundance of bacteria that is needed. Probiotics also stimulate the immune system by increasing anti-viral and natural killer T cell activity.