The immune system
The immune system is an intricate body system that plays multiple roles in each moment of our lives. Our nervous, digestive and endocrine systems are connected to the immune system. There is a cross-talk between the gut and the immune system, and approximately 70% of the immunity occurs in the gut. Since the 1980’s we have been aware that many immune cells produce hormones.
The organs of the immune system include the stomach, the GI tract, the thymus, the bone marrow, the spleen and the lymphatic system. The immune system cells are called leukocytes or white blood cells. The more specialized white blood cell is called lymphocytes, or T cells and B cells.
Proteins called cytokines are the hormones of the immune system, allowing communication both internally within the system and externally between the immune system and other body systems. The ‘C-reactive protein’ also plays a significant role in immune function. This is witnessed in the acute rise of the C-reactive protein in our blood during infection or inflammation.
The most known immune barrier is the skin. But we also have the cilia in our nose and lungs and the mucous we carry. These tiny barriers are potent first-line defence of the immune system. The hairs and sticky mucous help trap microorganisms and shuttle them out of our airways. Another barrier includes the acid present in our stomach. The hydrochloric acid released during meals should be so acidic that it will effectively kill microbes that we don’t want travelling to our GI tract – highly effective barrier protection. Our saliva, sweat, and earwax are also significant immune barriers. These secretions contain bacteria-killing enzymes that help us fight infections.
Our innate or non-specific immunity is the fast, first-wave response we have to any invader that makes it past our barrier defences. Innate immunity consists of a wide range of chemical signals, proteins and cells that quickly make their way to the site of infection. Natural killer cells are accurate to the name. They release enzymes and other substances that immediately damage pathogens. However, along with the innate dendritic cells, they act as messengers to the adaptive immune system, providing information and direction for more specific immune action.
Our adaptive immune system is evolutionarily younger than our innate immunity, appearing less than 500 million years ago. While innate immunity is found to some degree in all organisms, adaptive immunity exists only in vertebrates. Along with the nervous system, the abductive branch of our immune system is capable of remembering.
These two systems are unique in this capacity and provide beneficial services. Once our adaptive immune system encounters a pathogen, such as a virus, memory cells are created. These cells live for many years, sometimes decades, and respond quickly if reinfection occurs. Specialized white blood cells, called lymphocytes, make up most of our adaptive immunity. T cells and B cells play multiple roles in our specific immune actions. They identify and adapt to invaders, carry out their destruction, and communicate with other parts of the immune system to report and remember the invaders in the case of future infection.
T-cells and B-cells cooperate in an intricate immune dance that protects us and helps us to maintain a balanced immune response.