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Study links muscle mass with strong immune system

Study links muscle mass with strong immune system

That good physical health, obtained by strong muscles and skeletal system, is a byproduct of regular exercise and the right nutrition is no secret. The human body is built for regular movement, and movement through exercise helps regulate several bodily functions, helps maintain healthy body weight and lowers the risk of several diseases and keeps infections at bay.
Several studies have been performed to establish this aspect and benefits of exercise for the longevity of human life. And new research—published in the journal Science Advances that was published earlier this month, explains just that, especially in the case of chronic illnesses.
The study looked at the relationship between skeletal muscles and the condition of cachexia, in which the muscles and fat in the body waste away as an after-effect of severe chronic illness. This condition also severely weakens the immune system of the body as a result.
Cachexia is a common condition that affects people suffering from severe forms of illnesses such as the various types of cancers. The National Cancer Institute of the United States estimates that almost one-third of all cancer deaths are as a result of the wasting syndrome of cachexia, which is characterised by a dramatic loss of skeletal muscle mass and substantial weight loss.
Cachexia usually occurs in advanced stages of cancer and is most commonly seen in cases of pancreas cancer, stomach cancer, lung cancer, oesophageal cancer, colorectal cancer and head and neck cancer. In cachexia, the muscles and fat tissues of the body break down irreparably, leaving patients so frail that they are barely able to walk.
A 1993 study published in Nature had first highlighted the T-cell exhaustion that took place during severe chronic infections that pointed towards the development of conditions such as cachexia.
Another research published in the American Journal of Physiology, Endocrinology and Metabolism in 2013 also established a close relationship between another type of immune cells of the body (microphages) and muscle cells. This study, however, focused on skeletal muscle inflammation due to regular exercise, muscle damage or regeneration, or even inflammation arising out of obesity.
It also found that skeletal muscles contain resident immune cells and employ more when muscles contract and expand during exercise and muscle building. It is the skeletal damage during exercise that triggers the strengthening and growth of the muscles that prevents future damage.
The immune system of the human body is what protects us from attacks by bacteria, viruses, parasites and various other pathogens. The immune system is made up of several tiny cells and tissues, which guard against invading pathogens and prevent them from infecting the body. Even the dead cells of the human body, or the malfunctioning ones, are identified by the immune system and replaced by healthy, functioning ones.
The latest study, performed by scientists at the German Cancer Research Center in Heidelberg performed a series of tests on mice to evaluate how muscle mass is responsible for a robust immune system in the body. Some of the cells responsible for a strong immune response against illnesses in the body are known as T cells, which become impaired or weakened by cachexia.
Many viral infections and diseases such as cancers result in the overwhelming loss of body weight that also leads to muscle atrophy, the primary cause of cachexia. A type of T cells known as CD8+ become impaired during such infections, which is the common factor between the condition and the loss of muscle mass in the body.
The mice in the study were infected with the lymphocytic choriomeningitis virus in order to study the gene expression in their skeletal muscles. They observed that when the infection attacked the muscle cells of the mice, they began to release cytokines named interleukin-15 (IL-15), which is responsible for the development of inflammatory and protective immune responses to pathogens.
The IL-15 are a type of proteins or peptides that regulate cell response and act as precursors of T cells in the skeletal muscles of the body. When the body is attacked by a pathogen, they protect the T cells fighting the infection. According to the lead scientist of the study, the precursor cells can migrate from the muscles and develop into T cells to replace the ones that are losing their function while fighting the infection.
The study found out that mice that had more muscle mass were able to deal with the viral infection more effectively than those who had weaker muscles. The researchers, however, did not surmise that this would hold true even in the case of humans, and that further research was necessary to establish this relationship.
The scientists were also not able to ascertain how these precursor cells developed in the skeletal muscle mass that preserve the functioning of the T cells, sustaining the immune response for a longer period of time.

Several types of cells, proteins, tissues and organs make up the body's immune system, which not only helps identify any foreign body entering the system but also fights off pathogens that attack the body as well. The white blood cells (WBC), also known as leukocytes, run through the blood vessels all over the body and multiply when they come across a pathogen trying to cause an infection.
The leukocytes are further divided into two main types, known as phagocytes that absorb pathogens to kill them off, and lymphocytes, which aid the body in remembering previous pathogens and infections, helping to identify them in case of a recurrence. It is these lymphocytes that also become T lymphocytes or T cells. The T cells also have two different types: the helper T cells that are responsible for the immune response and killer T cells, which attack and kill off other cells, and take charge while fighting off viruses.
The lymphocytes, in turn, are responsible for identifying the antigen entering the body and releases antibodies to fight them off, and the B lymphocytes or the B cells are responsible for this function. 
Immunity of a human body is subdivided into further types, such as the immunity we are all born with, some that are acquired with age and vaccination, and passive immunity, which is taken from another source, like a newborn baby which gets this from the mother through the placenta as well as breast milk after birth.
Another study, published in 2016 in the journal Immunity, found out that certain immune cells in the body also produce certain types of protein that lead to the formation of new muscle fibres, especially after suffering a muscle injury or tear. 
A study published in the Journal of Sport and Health Science in 2019 also found that acute exercise improves the immune response and the body's defence activity, and that regular exercise improves immune regulation in the body while delaying age-related degeneration and dysfunction.