We develop immunity when we are exposed to a disease and our immune system is able to develop memory cells. The immune response to a secondary infection of the same pathogen will thus be stronger and faster because of these immune memory cells.
One of the most important characteristics of the immune system is its ability to discriminate between healthy body cells and foreign infected cells. Immune cells are able to make this distinction because they are able to interpret antigens on the surface of cells as either being foreign or as being self. Antigens could be thought of as name tags because they identify each specific cell by displaying its distinguishing protein. Immune cells recognize the body's own antigens as being different from invader cells because of the receptors they carry on their surfaces. The receptors of T-cells are able to recognize specific antigens which identify a vast number of invaders as targets. The T-cell receptors enable the cell to recognize and read the antigen that is on the body's own healthy cells and thus leave them alone. While maturing in the thymus, T-cells that react erroneously to an antigen made by the body, or "self," it will die off. In this way, T-cells with the potential to attack the body's own tissue are filtered out and do not survive. B- cell have a similar testing process in the bone marrow. As a result, T-cells and B-cells of the immune system are able to distinguish between the " self "and the invader, healthy body tissue versus pathogens; protecting healthy cells by targeting and eliminating infected cells and invaders.
Errors in this recognition process can result in autoimmune diseases like multiple sclerosis and rheumatoid arthritis.
Antibodies are proteins produces by the B-cells in our body as a response to an antigen. Antibodies all have a similar shape, like a "Y" . However, the shape of the top of the "Y" is directly related to the specific antigen that it is responding to. Our body can produce almost an infinite number and variety of antibodies. The antibodies dock, or attach to an antigen which marks it for destruction by macrophages. In addition, antibodies also clump around an antigen rendering it inactive.
Cells of the Immune System
The immune system is made up of a multifaceted defense system involving many different types of white blood cells. These white blood cells, or leukocytes, each have specific jobs and have a life span of about 24 hours. White blood cells are made in the red bone marrow from stem cells. Each of the specialized immune cells originate in the bone marrow and develops through an evolving sequence that produces a highly specialized range of immune cell equipped to carry out participate in this sophisticated defense system. These cells include, monocytes and neutrophils, which are specialized phagocytes, as well as eosinophils and basophils which are involved in the inflammatory response.
Furthermore, B-cells and T-cells originate as stem cells in the bone marrow however, they leave the bone marrow before they are fully mature. T-cells, or lymphocytes, leave the bone marrow and travel to the thymus where they fully mature. Thus the "T" in T-cell stands for thymus. The T-cells are involved in the specific immune response, or third line of defense. The T-cells regulate the defensive actions of the B-cells and other cells in the immune response. There are many kinds of T-cells; examples of these cells are, killer T-cells, helper T-cells, and suppressor T-cells.
Another immune cell is called the macrophage, or large phagocytes.
Macrophage is Greek for "big eater"
which is exactly what the macrophage cell does. Macrophages are immune cells that are active in the third line of defense. They engulf, digest and destroy pathogens and infected cells such as viruses, bacteria, and microorganisms. They then display the antigen, or tiny parts of the pathogen, on their cell surface thereby activating a higher level of defense. Macrophages are called antigen-presenting cells. By displaying the antigen, macrophages are able to communicate vital specific information about to identity of the pathogen to the Killer T-cells. This communication will secure the information necessary for the identification, attack, and destruction of the pathogen by attacking Killer T- cells.
Activation Sequences of the T-cells and B-cells of the Immune System
T- Cells and B-Cells: Cell- Mediation Immunity & Humoral Immunity
The third line of defense and the two main immune responses are controlled by the T- cells and B-cell. These two responses are Cell- Mediation Immunity and Humoral Immunity. Both the T-cells and B-cells are lymphocytes, which are also referred to as white blood cells. These white blood cells are involved in the specific defenses of the immune system. Both the B- cells and T-cells have highly sensitive receptors, which allows them to recognize antigens. T-cells coordinate and regulate the responses of the immune system as well as attack infected cells. There are several kinds of T-cells.
B- cells are a type of white blood cell, that is made in the bone marrow. They are responsible for the Humoral response of the immune system. This means they are responsible for the immune activity in the body's fluids, or humors. These humors include, the blood, lymph, and body tissues. They are like the "Navy," patrolling the waters to keep us safe. When B- cells are activated by the T-helper cells, they differentiate into plasma cells which become antibody producing factories. B-cells produce specific antibodies for each particular antigen. B- Cells are capable of producing an infinite number of antibodies to different antigens. However, some B- cells do not turn into antibody factories, they become " memory cells" that will live for decades and are able to remember and recognize the antigens that they have been exposed to.
T-cells are a type of white blood cell that are responsible for the cell- mediated immune response. T-cell are able to produce Killer T-cells, which target and kill the cells that have already been infected in the body tissue. The Killer T- cell is a type of activated T- cell that will aggressively seek out, dock against, and kill infected cells.
The immune system is able to survey the inside of a cell by reading the proteins displayed on its surface. The protein HLA (Human Luekiside Antigen) is the protein that enables the cell to display the contents of the inside of a cell on its surface. T- cells read the HLA protein on the cell surface as either self or invader. In this way, a virus hidden within the contents of the host cell will be revealed. When these protiens are displayed on the surface, the T-cell reads them as being foreign, and destroys the infected cell.
Cells of the Immune System
When Things Go Wrong
The greatest challenges to global health involve illnesses that defy, test, trick, attack and disrupt the functions of immune system. When problems occur with our immune system, the results are dire. Often, death, chronic illness, and life altering disease are the effects of an immune system failure. Problems that occur with the immune system can be grouped into three main categories. These categories include autoimmunity, when the immune system attacks its own body; hypersensitivity, when the immune system is overly sensitive as in allergies; and immunodeficiency, when the immune system is weakened or unable to respond to antigen as in AIDS. The many reasons for each of these breakdowns of the immune system continues to be a challenge to the medical field. However, the field of bioengineering is offering new hope for those who suffer from illness that involve the immune system.
Autoimmunity is when the immune cells are unable to distinguish between; "self," or the body's own cells and a foreign invader. Because of this lack of recognition, the immune cells attack the healthy body tissue too. One examples of illness caused by autoimmunity is multiple sclerosis. In the case of multiple sclerosis, the immune T-cells attack the myelin sheath that covers and insulates the nerve cell. These immune cells fail to recognize the myelin as "self", or part of the body. Unable to discriminate between the body tissue and invader, the T-cells attack the myelin as foreign, which causes inflammation and break down of the nerve tissue. As part of this response, the inflammation of the myelin can cause blockages or short circuit of neural communication. Signals from the affected nerves are not able to travel to and from the brain as needed resulting in disease symptoms. There are many symptoms which can be debilitating and often confine one to a wheelchair. There is no cure for MS.
Hypersensitivity is an immune disorder cause by a heightened response to a non-threatening substance. For example, an allergy is a problematic response by the immune system to peanuts, pollen, eggs or mold, just to name a few. The immune system responds to the foreign substance as if it is a threatening pathogen. In this response, b-cell make antibodies to attack the allergen causing itchy watery eyes, inflammation of the skin, digestive system, airways, and /or sinuses.
Immunodeficiency, or immunosuppression, is a condition where the immune system is not responding to an antigen effectively. This condition may be caused by a direct attack on the immune system or a congenital defect, the effect cripples the ability of the immune system to function properly. As a result, the affected person is left unprotected and vulnerable to a myriad of pathogens. Because of this, often a secondary infection can become life threatening. One example of an immunodeficiency disease is IgA. Those with IgA deficiency are unable to make IgA antibodies. Severe Combined Immunodeficiency Syndrome (SCID) is another example of a rare, but very serious immunodeficiency disease of the immune system. Babies born with this disease do not live very long because they do not have any B-cells or T-cells leaving them defenseless against pathogens. The treatments have been limited to bone marrow transplants and to, literally, put the child in a sterile, plastic bubble as protection.
In 1976 the movie, The Boy in the Plastic Bubble, was written and inspire by the real life stories of Davis Vetter and Ted DeVita who suffered from immunodeficiency.
AIDS (acquired immunodeficiency syndrome) is an deadly immunodeficiency illness. It is the caused by the human immunodeficiency virus (HIV). The HIV virus directly attacks the immune system. The T- helper cell is the target of this virus. The virus invades the T- helper cells using the T-cell as its host. The HIV virus replicates itself within the host helper T-cell until the cell membrane explodes. With this explosion, the host helper T-cell is destroyed. At the same time, a fleet of new viral, HIV, pathogens are released to infect new helper T- cells. As a result, the immune response is compromised further as the disease progresses. This is because the helper T-cell is an important immune cell that is vital to initiating the immune response. The body's immune response is slowly eroded and is unable to launch an attack on invading pathogens. This leaves the infected person vulnerable to a secondary infection. As a result, of the weakened immune system, a minor exposure or infection can become life threatening. The HIV and AIDs viruses are spread by sexual contact or by infected blood or body fluids. It can take many years for one to show symptoms of the disease, which can be dangerous for the spread of the disease and the important health care of those infected. The disease has devastated many populations. Although there is no cure for HIV/AIDS, we now have medications that can slow the progression of HIV. There is greater hope now for improved therapies in the field of bioengineering.
Another problematic example of the immune system involves transplant rejection. Organ transplants are challenging because the immune system views the new organ as an invader. Although the immune system is doing exactly what it is supposed to be doing, this response can cost one a lifesaving organ transplant. Extreme care is given to matching and typing tissue as a way of preventing transplant rejection. If the immune cell receptors of the host person latch onto antigens from the organ transplanted and recognize it as non-self, then the immune system will react against the organ, attacking the transplanted organ. This response is like friendly fire, the immune system accidently attacking its own lifesaving organ. Immunosuppressant drugs are used to reduce transplant rejection, but these turn off the immune system and create other risks.
Applying the concepts of bioengineering to the immune system could offer relief and hope for those who suffer from these chronic and debilitating diseases and offer solutions that could, cure, or inhibit the progression of these illnesses. Could these answers lie in new ways to enhance, strengthen, or reinforce these mighty fighters to create a fleet of super cells?