Friday, April 29, 2011

IX. Immune System

An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens, including bacteria, virus, parasites, etc. and tumor cells, including irregular cells growth, cancer cells to keep us healthy. In most cases, the immune system does a great job of keeping people healthy and preventing infections. But sometimes problems with the immune system can lead to illness and infection.

1. Immune system and functioningAlthough immune system have done a great job in protecting us against foreign invasion, but unfortumately, during process od their functions, they may induce the production of free radicals and chain of free radicals that can be harmful to our body.
a. Red and white blood cells
During the process, the tissue of bone marrow of the long bone produce stem cells which will evolve into progenitor cells. This progenitor cells finally differentiate into white and redblood cells. While the red blood cells deliver oxygen (O2) and nutrients to the body tissues via the blood flow through the circulatory system, the white blood cells or leukocytes are cells of the immune system involved in defending the body against both infectious disease and foreign materials.

b. Thymus gland
The thymus gland a specialized organ form part of the immune system. It helps in the production and functioning of T-lymphocytes (T cells), which are critical cells of the adaptive immune system by providing an inductive environment for development of T-lymphocytes from hematopoietic progenitor cells. The thymus gland starts to shrink from the time when we was born and by age of 60, it had shriveled away to almost nothing.
Beside it is important to the functions of above, it also produced varies protein hormones, such as IL-2, is a protein manufactured by lymphocytes. Peripheral blood obtained from patients with chronic hepatitis B and viral infections responded to THF with increased production of IL-2. This suggests a possible antiviral role for this thymic hormone, and is one of the reasons we should replace thymic hormone as we pass the second decade.

c. Lymphatics system
The lymphatic system form part of the immune system comprising a network of conduits called lymphatic vessels that carry a clear fluid called lymph unidirectionally toward the heart. Beside having a function of removing interstitial fluid from tissues, absorbing and transporting fatty acids and fats from the circulatory system and transporting immune cells to and from the lymph nodes into the bones, it also enhances the immune system of the body by defending the body against the infections and spread of tumors due to its connective tissue with various types of white blood cells enmeshed in it, most numerous being the lymphocytes.

d. Spleen
Spleen formed part of immune system, is imporant in the filtration process of removal of old or damaged red blood cells from the circulation and filters out bacteria of the blood. The immunological function of spleen in human body is looked after by the white pulp which consists of aggregates of lymphoid tissue. Abnormal function of spleen can result in enlarged organ due to its inability to perform function of removing of old or damaged red blood cells, leading to accumulation or trapping of red blood cells, causing major turmoils in immune system.

2. Types of free radicals utilized by Immune system
Free Radicals play an important role in the function of the Immune System. The immune systen produce free radicals to kill foreign microbes, but the production of free radical sometime can be excessive, leading to formation of a large number of free radicals that stimulate the formation of more free radicals, leading to even more damage, until they are brought to stop.

a. Nitric oxide
Nitric oxide is also generated by phagocytes of immune system as part of the human immune response. It is produced as free radicals and toxic to bacteria, that helps the immune system in regulating the armamentarium of phagocytes that play a role in inflammation.
Nitric oxide can contribute to reperfusion injury if excessive amount produced during reperfusion and reacts with superoxide to produce the damaging oxidant peroxynitrite.

b. Superoxide
Superoxide is a compound that possesses the superoxide anion with the chemical formula O2−. It is biologically quite toxic and is deployed by the immune system to kill invading microorganisms produced in large quantities by the enzyme NADPH oxidase.
If over produce, superoxide may contribute to the pathogenesis of many diseases , such as radiation poisoning and hyperoxic injury and aging as aresult of oxidation.

c. Neutrophils
Neutrophils, the phagocytes can internalize and kill microbes, but each phagocytic event causes the formation of a phagosome into which reactive oxygen species (ROS) and hydrolytic enzymes are secreted, leading to respiratory burst, resulting in activating the enzyme NADPH oxidase, which produces large quantities of superoxide.

d. Chain reaction
Since free radicals are caused by the body’s own natural processes by stealing oxygen electron from other cell, its chain effect result in production of even more free radicals. These aditional free radicals continue until they are stopped, leading to toxins, radiation, etc. that weakens the immune system.

e. Etc.

3. How free radicals affect Immune system
There are many factors which affect immune system as we age. Hormone declining such as human growth hormone and Dehydroepiandrosterone (DHEA) are the major influences. In factor, some researchers suggested free radicals is one of major contribution to the declining of immune system.
a. Thymus
The declining of the thymus function contributes a direct effect on the immune system due to diminish of quantity of T cells and immune factors.

b. Lipid peroxidation
Researchers found that lipid peroxidation are able to attack immune cells membrane, leading to the impediment of cells membrane activities, causing susceptibility diseases found in aging person.

c. NADHP oxidase
NADHP oxidase (nicotinamide adenine dinucleotide phosphate-oxidase) is a membrane-bound enzyme complex found in the plasma membrane. Free radicals cause damage to membrane, leading to diminish of its function in fighting against foreign invasion.

d. Cytokine
Free radicals damage immune cells that affect the function of cytokines in transmitting intercellular signals, leading to many disease states and conditions ranging from major depression and Alzheimer's disease to cancer.

e. Etc.

4. antioxidants and immune system
Enzyme antioxidants, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase are best known to defense our body in fighting or scavenging against forming of free radicals by neutralizing them. Other antioxidants include
a. Zinc
Zinc, as a antioxidant is essential mineral in ading immune system by enhancing the peoper function of T cells which belong to a group of white blood cells known as lymphocytes, in fighting against damaging free radicals.

b. Selenium
Selenium is one of the powerful antioxidant. In the extracellular space, it helps to influence immune processes by proliferating the response to mitogen, and macrophages, leukotriene.

c. Vitamin A
vitamin A plays an essential roles in enhancing a broad range of immune processes, including lymphocyte activation and proliferation, T-helper-cell differentiation, the production of specific antibody isotypes and regulation of the immune response.

d. Vitamin C
Researchers found that vitamin C raised the concentration in the blood of immunoglobulin A, M that promotes the ability of antibodies and phagocytic cells to clear pathogens.

e. Vitamin E
In aged mice study showed that Vitamin E beside increased both cell-dividing and IL-producing capacities of naive T cells it also enhances the immune functions in association with significant improvement in resistance to influenza infection.

f. Carotenoids
Carotenoids reduces oxidation damage to cells and protects LDL cholesterol from oxidation, thus reducing the risk of aging and chronic diseases caused by damaging free radicals.

g. Etc.