Macrophages are the body's first line of defense and have many roles. A macrophage is the first cell to recognize and engulf foreign substances antigens. Macrophages break down these substances and present the smaller proteins to the T lymphocytes. T cells are programmed to recognize, respond to and remember antigens. Macrophages also produce substances called cytokines that help to regulate the activity of lymphocytes. Dendritic cells are known as the most efficient antigen-presenting cell type with the ability to interact with T cells and initiate an immune response.
Dendritic cells are receiving increasing scientific and clinical interest due to their key role in the immune response and potential use with tumor vaccines. There are different types of white blood cells that are part of the immune response. Neutrophils or granulocytes are the most common immune cells in the body.
With an infection, their number increases rapidly. They are the major components of pus and are found around most common inflammations. Complement proteins can also assemble on the surface of microorganisms forming a complex. This complex can then puncture the cell wall of the microorganism and destroy it. Our bodies are covered with bacteria and our environment contains bacteria on most surfaces.
Our skin and internal mucous membranes act as physical barriers to help prevent infection. When the skin or mucous membranes are broken due to disease, inflammation or injury, bacteria can enter the body. Infecting bacteria are usually coated with complement and antibodies once they enter the tissues, and this allows neutrophils to easily recognize the bacteria as something foreign.
Neutrophils then engulf the bacteria and destroy them Figure 4. When the antibodies, complement, and neutrophils are all functioning normally, this process effectively kills the bacteria.
Most of us are exposed to viruses frequently. The way our bodies defend against viruses is different than how we fight bacteria. Viruses can only survive and multiply inside our cells. When a virus infects a cell, the cell releases cytokines to alert other cells to the infection. Unfortunately, many viruses can outsmart this protective strategy, and they continue to spread the infection. Circulating T-cells and NK cells become alerted to a viral invasion and migrate to the site where they kill the particular cells that are harboring the virus.
This is a very destructive mechanism to kill the virus because many of our own cells can be sacrificed in the process. Nevertheless, it is an efficient process to eradicate the virus. At the same time the T-lymphocytes are killing the virus, they are also instructing the B-lymphocytes to make antibodies. When we are exposed to the same virus a second time, the antibodies help prevent the infection. Memory T-cells are also produced and rapidly respond to a second infection, which also leads to a milder course of the infection.
In most instances, bacteria are destroyed by the cooperative efforts of phagocytic cells, antibody and complement. The phagocytic cell then begins its attack on the microbe by attaching to the antibody and complement molecules. Phagocytosis of the Microbe: After attaching to the microbe, the phagocytic cell begins to ingest the microbe by extending itself around the microbe and engulfing it. Destruction of the Microbe: Once the microbe is ingested, bags of enzymes or chemicals are discharged into the vacuole where they kill the microbe.
Immune deficiencies are categorized as primary immune deficiencies or secondary immune deficiencies. Secondary immune deficiencies are so called because they have been caused by other conditions. Secondary immune deficiencies are common and can occur as part of another disease or as a consequence of certain medications.
The most common secondary immune deficiencies are caused by aging, malnutrition, certain medications and some infections, such as HIV. The most common medications associated with secondary immune deficiencies are chemotherapy agents and immune suppressive medications, cancer, transplanted organ rejection or autoimmune diseases. Other secondary immune deficiencies include protein losses in the intestines or the kidneys. When proteins are lost, antibodies are also lost, leading to low immune globulins or low antibody levels.
Regardless of the root cause, recognition of the secondary immune deficiency and provision of immunologic support can be helpful. The types of support offered are comparable to what is used for primary immune deficiencies. The primary immunodeficiency diseases are a group of disorders caused by basic defects in immune function that are intrinsic to, or inherent in, the cells and proteins of the immune system.
There are more than primary immunodeficiencies. Some are relatively common, while others are quite rare. Some affect a single cell or protein of the immune system and others may affect two or more components of the immune system.
Although primary immunodeficiency diseases may differ from one another in many ways, they share one important feature. They all result from a defect in one or more of the elements or functions of the normal immune system such as T-cells, B-cells, NK cells, neutrophils, monocytes, antibodies, cytokines or the complement system.
In these disorders, the cause is unknown, but it is believed that the interaction of genetic and environmental factors may play a role in their causation. Because the most important function of the immune system is to protect against infection, people with primary immunodeficiency diseases have an increased susceptibility to infection.
This may include too many infections, infections that are difficult to cure, unusually severe infections, or infections with unusual organisms. The infections may be located anywhere in the body. Common sites are the sinuses sinusitis , the bronchi bronchitis , the lung pneumonia or the intestinal tract infectious diarrhea.
Examples of foreign material can be microorganisms, pollen or even a transplanted kidney from another individual. In some immunodeficiency diseases, the immune system is unable to discriminate between self and non-self. In these cases, in addition to an increased susceptibility to infection, people with primary immunodeficiencies may also have autoimmune diseases in which the immune system attacks their own cells or tissues as if these cells were foreign, or non-self.
There are also a few types of primary immunodeficiencies in which the ability to respond to an infection is largely intact, but the ability to regulate that response is abnormal.
Primary immunodeficiency diseases can occur in individuals of any age. The original descriptions of these diseases were in children. However, as medical experience has grown, many adolescents and adults have been diagnosed with primary immunodeficiency diseases. This is partly due to the fact that some of the disorders, such as CVID and Selective IgA Deficiency, may have their initial clinical presentation in adult life. Effective therapy exists for several of the primary immunodeficiencies, and many people with these disorders can live relatively normal lives.
Primary immunodeficiency diseases were initially felt to be very rare. However, recent research has indicated that as a group they are more common than originally thought. It is estimated that as many as 1 in every 1,—2, people may have some form of primary immunodeficiency. This page contains general medical information which cannot be applied safely to any individual case. Medical knowledge and practice can change rapidly. Therefore, this page should not be used as a substitute for professional medical advice.
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Organization and Development of the Immune System The immune system is a wonderful collaboration between cells and proteins that work together to provide defense against infection.
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More Actions. For Patients and Families. More Resources. Our white blood cells are stored in different places in the body, which are referred to as lymphoid organs. These include the following:. These cells surround and absorb pathogens and break them down, effectively eating them. There are several types, including:. Lymphocytes help the body to remember previous invaders and recognize them if they come back to attack again.
Lymphocytes begin their life in bone marrow. Some stay in the marrow and develop into B lymphocytes B cells , others head to the thymus and become T lymphocytes T cells. These two cell types have different roles:. The immune system needs to be able to tell self from non-self. It does this by detecting proteins that are found on the surface of all cells.
It learns to ignore its own or self proteins at an early stage. In many cases, an antigen is a bacterium, fungus, virus, toxin, or foreign body. But it can also be one of our own cells that is faulty or dead. Initially, a range of cell types works together to recognize the antigen as an invader. Antibodies are special proteins that lock on to specific antigens. Each B cell makes one specific antibody. For instance, one might make an antibody against the bacteria that cause pneumonia , and another might recognize the common cold virus.
Antibodies are part of a large family of chemicals called immunoglobulins, which play many roles in the immune response:. Antibodies lock onto the antigen, but they do not kill it, only mark it for death.
The killing is the job of other cells, such as phagocytes. Helper T cells Th cells — they coordinate the immune response. Some communicate with other cells, and some stimulate B cells to produce more antibodies. Others attract more T cells or cell-eating phagocytes. Killer T cells cytotoxic T lymphocytes — as the name suggests, these T cells attack other cells. They are particularly useful for fighting viruses. They work by recognizing small parts of the virus on the outside of infected cells and destroy the infected cells.
Once an antibody has been produced, a copy remains in the body so that if the same antigen appears again, it can be dealt with more quickly. That is why with some diseases, such as chickenpox , you only get it once as the body has a chickenpox antibody stored, ready and waiting to destroy it next time it arrives.
This is called immunity. We are all born with some level of immunity to invaders.
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