What is the Immune System?

An immune system is a collection of biological processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms collectively called antigens, and needs to distinguish them from the organism's own healthy cells and tissues in order to function properly.

When a pathogen enters the blood stream, immune cells are activated. There are several types including the polymorphonuclear cells that form pus. Others - B-cell lymphocytes identify pathogens and mark them as targets for T-cell lymphocytes. Helper T-cells alert immune cells to join the battle, killer T-cells destroy the invader and suppressor T-cells switch off the immune response when the job is done.

B-cells are lymphocytes that play a large role in the humoral immune response (as opposed to the cell-mediated immune response, which is governed by T cells). The principal functions of B cells are to make antibodies against antigens, perform the role of Antigen Presenting Cells (APCs) and eventually develop into memory B-cells after activation by antigen interaction. B-cells are an essential component of the adaptive immune system. Immature B-cells are produced in the bone marrow of most mammals. After reaching the immature stage in the bone marrow, these immature B-cells migrate to the spleen, where they are called transitional B cells, and some of these cells differentiate into mature B lymphocytes. When B cell receptors on the surface of the cell matches the detected antigens present in the body the B-cell proliferates and secretes a free form of those receptors (antibodies) with identical binding sites as the ones on the original cell surface. After activation, the cell proliferates and B memory cells would form to recognise the same antigen. This information would then be used as apart of the adaptive immune system for a more efficient and more powerful immune response for all previously encountered antigens.

Helper T-cells are a sub-group of lymphocytes (a type of white blood cell or leukocyte) that plays an important role in establishing and maximizing the capabilities of the immune system. These cells are unusual in that they have no cytotoxic or phagocytic activity - they cannot kill infected host cells or pathogens, and without other immune cells they would usually be considered useless against an infection. T helper cells are involved in activating and directing other immune cells, and are particularly important in the immune system. They are essential in determining B-cell antibody class switching, in the activation and growth of Killer T-cells and in maximizing bactericidal activity of phagocytes. It is this diversity in function and their role in influencing other cells that gives T helper cells their name. The abbreviation T, in T cell, stands for thymus, since this is the principal organ responsible for the T cell's maturation.

A cytotoxic T cell (also known as T-Killer cell or killer T cell) belongs to a sub-group of T lymphocytes (a type of white blood cell) that are capable of inducing the death of infected somatic or tumor cells; they kill cells that are infected with viruses (or other pathogens), or are otherwise damaged or dysfunctional. Killer T-cells are recognized as such cells once they become activated and are generally classified as having a pre-defined cytotoxic role within the immune system.

Suppressor T-cells (also known as T regulatory cells) are a component of the immune system that suppress immune responses of other cells. This is an important "self-check" built into the immune system so that responses do not go haywire. These cells are involved in closing down immune responses after they have successfully tackled invading organisms, and also in keeping in check immune responses that may potentially attack one's own tissues (autoimmunity). To function properly, the immune system must discriminate between self and non-self. When self/non-self discrimination fails, the immune system destroys cells and tissues of the body and as a result causes autoimmune diseases. Regulatory T cells actively suppress activation of the immune system and prevent pathological self-reactivity, i.e. autoimmune disease. The critical role regulatory T cells play within the immune system is evidenced by the severe autoimmune syndrome that results from a genetic deficiency in regulatory T cells.

An important question in the field of immunology is how the immunosuppressive activity of regulatory T cells is modulated during the course of an ongoing immune response. While the immunosuppressive function of regulatory T cells prevents the development of autoimmune disease, it is not desirable during immune responses to infectious microorganisms. Current hypotheses suggest that upon encounter with infectious microorganisms the activity of regulatory T cells may be downregulated, either directly or indirectly, by other cells to facilitate elimination of the infection. Experimental evidence from mouse models suggests that some pathogens may have evolved to manipulate regulatory T cells to immunosuppress the host and so potentiate their own survival. For example, regulatory T cell activity has been reported to increase in several infectious contexts, such as retroviral infections (the most well known of which is HIV), bacterial infections (like tuberculosis), and various parasitic infections including malaria.

For additional information on the Immune System and how it works visit the US Department of Health and Human Services. Click here to read the article.

One more good resource on the topic of Immune System and its components can be accessed here.

The healthy immune response can be compromised. When this system is disrupted the doors to infection open and health is compromised. For example, HIV destroys helper T-cells and leaves killer T-cells cut off and powerless. As a result, invading micro-organisms that the body would normally get rid off are able to cause severe infections that characterize AIDS.

Healthy growth and activity of immune cells depends on many things, one of which is the availability of Glutathione (GSH). Dr. Gustavo Bounous, a leading expert on GSH says: “The limiting factor in the proper activity of our lymphocytes is the availability of GSH”.

Experimental depletion of GSH severely diminishes the ability of these cells to fight pathogens and leaves the door open for the disease. In numerous studies the level of intracellular GSH in the lymphocytes corresponds directly to the effectiveness of the immune response. In the simplest form Glutathione is a sort of “food” for the immune system.

When a lymphocyte attacks a pathogen, it releases powerful oxidizing chemicals such as peroxide and protects itself against these chemicals by neutralizing them with GSH. In addition, lymphocytes must replicate themselves over and over again in order to attack the whole pathogen population. This requires the use of oxygen and releases further oxidants. In order to continue multiplying efficiently Glutathione is once again required to counteract the effects of oxidation. So fighting off infection consumes GSH in two ways – by using it to stabilize free radicals and also to grow immune cells. The protective activity of GSH is two-fold – it enhances the activity of immune cells and also functions as an antioxidant within them.

Glutathione is at the heart of all immune functions and low GSH levels are seen in many diseases especially AIDS. Raising and maintaining GSH levels can minimize the risk of these diseases. Although only very ill people are severely deficient in Glutathione, those in good or fair health can benefit from raising Glutathione levels, especially in these days when we are exposed as never before to environmental toxins and newly emerged drug-resistant bacteria.

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