B Lymphocytes
They recognize foreign proteins from the disease organisms, these are known as the antigens, which differ from the natural bodies protein. The antigens trigger the B cells to enable them to multiply. They begin as stem cells in the bone marrow and then develop into lymph nodes.
T Lymphocytes
They attach themselves to the infected target cells after they have recognized the antigens on the surface. The T cells attack cancer cells to enable the tumours growth to become slower. They are able to survive for several years to allow it to respond if an antigen attempts a second invasion. They are also able to mobilize quickly. They develop inside the thymus gland and they react to the remains of the destroyed antigens attacking them as well as any infected cells.
The Lymphatic Role Within The Immunity
The lymphatic system has a role within the immunity via the lymphatic tissues which consist of capillaries, vessels and nodes. The capillaries drain water, protein, microbes and foreign materiel from between the cells into the lymph vessels. The vessels drain any of the remaining substances into the blood.
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The spleen, tonsils and thymus also have an important role in the immunity. The spleen helps the production of B and T cells, it removes the worn out red cells, it helps to filter bacteria and it is responsible for storing and releasing the blood. The tonsils filter out micro organisms that enter into the respiratory tract. The thymus is responsible for helping T cells to mature, producing the thyroxin hormone which stimulates the T cells and the lymph nodes to produce plasma cells that produces antibodies.
The Complement System
Within the blood there are approx 25 inactive proteins and these are known as the complement proteins and are activated by antibodies or lymphokines. They help to destroy bacteria, neutralizing their toxins and also clear away antigen and antibody complexes that trigger a cascade of complement proteins. They also attach themselves to diseased organisms. The proteins penetrate the cell membrane of the diseased organism which then bursts and dies as intracellular fluids flow in. if a global defence is breached then a global response to spreading infection occurs which causes an increase in white blood cells.
Infectious Organisms and Immunization
The body is constantly infected by bacteria, viruses, fungi and protozoa. Some are beneficial like the bacteria in the intestine which aids digestion. Others are harmful and cause illnesses from colds to tetanus which is a more life threatening illness.
Bacteria
Bacteria that are found in soil, water and air can cause serious illnesses, for example pneumonia, tetanus and syphilis. Antibodies are affective against most bacteria as they destroy most of the bacterial wall. Vaccines can also combat some bacterial infections like tetanus and haemophilus influenza.
Some bacteria invade tissue cells while others produce poisonous substances called toxins. Some toxins are dangerous. Toxins change certain chemical reactions in cells causing disruption in their normal function. The diphtheria toxin damages the heart muscle by inhibiting protein synthesis. Some toxins cause the blood to clot within the smaller blood vessels which causes the vessels to become deprived of blood therefore causing damage. Some toxins also damage the cell walls of the blood vessels which results in leakage causing the blood pressure to decrease and eventually leads to the heart not being able to transport the correct amount of blood to the brain.
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Many bacteria form intricate ways to resist antibodies. The most effective is transferring small packages of the DNA cell, known as plasmids, between bacterial populations. The bacteria that receive plasmids inherit the resistant gene and it develops the same resistance that the donor bacterium has.
Plasmids send a signal to the bacteria for it to produce enzymes that inactivate drugs. They sometimes stimulate a bacterium to change its receptor sites. The plasmid transfer takes place during a process known as conjugation. The transfer produces a large population of bacteria which forms enzymes against antibodies.
Viruses
Unlike bacteria viruses are unable to be destroyed by antibodies. The body must produce specific antibodies to combat every virus. Billions of viruses cover a small area the size of a pin head. Infections from these viruses can cause a variety of diseases. Including colds, polio and AIDS. Viruses are unable to reproduce on their own because they only have a few genes. They are also unable to process nutrients independently. To ensure they live and reproduce they have to invade the host cells that either die or have an abnormal function. Some viruses order the immune system to kill normal cells.
The proteins surface has to attach itself to the receptor sites on the surface before the virus is able to invade. When it is attached the virus penetrates the host cell and the protein shell releases its nucleic acid. This acid uses the host cells raw material and possibly enzymes to make replicas of it. The replicated acid then generates new virus particles. The new particle makes the cell swell and therefore may cause it to burst or maybe die. If the cell bursts it releases particles that affect other cells, however not all viruses destroy cells for example the herpes virus which form buds and then removes part of the cells membrane which are known as enveloped viruses.
The influenza virus has three types – A, B and C – each one is able to change its structure. Infection can re-occur when antibodies that defends the body against a previous viral structure that could be ineffective by new ones. This is called antigenic shift and occurs in antigens where the antibodies attach. Viruses can be recognised as RNA, DNA and viruses.
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Adeno viruses – DNA – infects the tonsils, respiratory tract and the eyes
Papova viruses – DNA – initiates benign or non cancerous tumours like warts on the hands and feet
Herpes viruses – DNA – causes cold sores, herpes, chicken pox, shingles and glandular fever
Corona viruses – RNA – causes colds
Picorna viruses – RNA – causes polio, viral hepatitis and a form of meningitis
Retro viruses – RNA – able to convert DNA into RNA and can cause AIDS as well as leukaemia
Reo viruses – RNA – causes respiratory infections and gastroenteritis
Orthomyxo viruses – RNA – causes influenza that includes fever, cough and sore throat
Paramyxo viruses – RNA – causes mumps, measles, rubella and croup
Protozoa
A primitive, single celled animal, some are parasites that can cause disease in humans. They have no cell walls and many have one or more appendages called flagella and they help with movement. Amoebae ingest red blood cells as well as food particles.
Protozoal parasites can cause malaria. Malaria has four types of plasmodia protozoan and is spread by a bite from a female mosquito and the symptoms are fever and chills. The plasmodium falciparum affects internal organs as well as the brain. If not treated with the correct medication immediately following a bite could be fatal. The parasites employ mechanisms that invade the immune system. The leishmania parasite is responsible for a disease called kala-azar that lives and multiplies in the blood cells that engulf micro organisms known as phagocytes.
Fungi
Fungi are organisms that scavenge dead or rotten tissue. Some fungi infect humans causing harmless diseases to the skin, nails and the mucous membranes. It can also cause fatal infections to various vital organs for example the lungs.
Cryptococcosis – causes meningitis, pneumonia and sometimes affects the skin as well as the bones
Aspergillosis – a fungal infection which spreads via ventilation and it affects the lungs
Dermatophytosis – a skin infection which is also known as tinea, it affects the scalp, feet and nails
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Histoplasmosis – it is associated with contaminated soil. The fungal spores are inhaled and can cause pneumonia and the spores can spread to organs like the heart causing infection
Fungal infections respond to antifungal drugs in several ways. Thrush will respond to local application of an antifungal drug. A person who has a lower immunity can catch a deep infection which requires longer therapy with a more toxic drug because they are more difficult to cure.
Immunization
Some diseases are common and can re-occur in the same person. Other infections will only occur once in a lifetime because the immune system remembers the organism and is able to resist infection. A person is protected against a disease when the immunization creates a memory before the disease has been obtained.
There are two types of immunization – active and passive. Active is where a vaccine containing pathogens is injected to stimulate the system to allow it to create antibodies. Passive involves injecting antibodies and gives short term protection.
Immune disorders
The body has defences that are provided by the immune system to fight against infection, cancer, injuries and the damages caused by poisonous and corrosive chemicals. The immune system has two types of disorders. With allergies and autoimmune disorders the immune system overreacts but with immunodeficiency diseases the defence system is weak and unable to cope with threats to its health.
The allergenic response
An allergy is a response from the immune system to a substance which is usually harmless. These substances are called allergens and can be inhaled, swallowed or direct contact to the eyes and skin. They provoke allergic responses like hay fever, rashes or asthma. People have allergies to various different things like eggs, milk, fish or even dust and pets.
Autoimmune disorders
Occasionally antibodies are formed against the bodies own tissues not against bacteria. This may be directed against particular organs like the thyroid gland or it may cause a general illness. It becomes more common in the middle aged and appears to affect woman rather than men.
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Addison’s disease
occasionally the adrenal glands become damaged which results in low blood pressure, weakness and in turn lowers the bodies ability of response to stress
Haemolytic anaemia
This autoimmune form of anaemia shortens the lifespan of the red blood cell and this causes loss of energy, headaches and breathlessness
Grave’s disease
The thyroid becomes overactive and enlarged which forms a goitre causing weight loss, restlessness and tremor
Multiple sclerosis
This causes muscles weakness, disordered sensations as well as speech and vision problems which is due to the coating of the nerve fibres becoming damaged
Myastheria gravis
This is damage to the nerves and muscles causing muscle weakness and fatigue
Systemic lupus erythematosus
Damaged connective tissues causes loss of function to the kidneys, joints and lungs
Addison’s disease
Hyposecretion of the adrenal hormones resulting in weakness, weight loss, loss of appetite, reduction in blood sugar and nausea
Cardiomyopathy
A disease of the cardiac muscle i.e. the myocardium, leading to heart failure
Ulcerative colitis
This affects the mucus cells of the colon and is a inflammatory disease which is recognized by diarrhoea with a showing of blood along with mucus or pus in the stools
Myxedema
A hyposecretion of the thyroid hormone causing a decrease in the metabolic rate which leads to weight gain, hair loss, edema and a reduction the mental and physical vigor
Rheumatoid arthritis
An inflammatory joint disease which causes inflammation spreading to various fibrous tissues
Reproductive infertility
This affects the antigens of the sperm or the tissues that surround the ovum and results with the inability to produce babies due to the destruction of gametes
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AIDS
AIDS is caused by the human immunodeficiency virus. The HIV virus destroys a certain lymphocyte, a certain white blood cell. The immune system becomes less affective as the cells decline. Eventually, after a long period of time, it will lead to death. The HIV virus is spread via sex or contaminated blood. Somebody who catches AIDS may not have any symptoms for many years and they are known as asymptomatic carriers. Towards the later stages the symptoms are weight loss, night sweats, fever and diarrhoea. When it is full on the infected person becomes susceptible to infections as well as certain cancers.
If AIDS damages the immune system the lungs develop infections. Patches appear on the skin that will gradually spread to the surface of the whole body and eventually to the internal organs. It also causes diarrhoea which is the most common symptom due to infection in the gastrointestinal tract with parasites. HIV can spread to the brain and nervous system which will cause mental disturbance, vision problems leading to blindness, weakness and paralysis.
The whole body and the immune system
The immune systems agents are antibodies, lymphocytes, substances and cells. They are found both inside and outside of the human body and are on guard at all times. The immune system is regulated by the nervous system and the endocrine system. These in turn are influenced by the feedback from different parts of the body.
SUMMARY
The immune is a collection of cells that keeps a note of the pathogens that invade and it is able to destroy them. This makes the body immune to that disease. The immune system is responsible for warding of infection through the infection fighting cells and chemicals.
References
- Anatomy & physiology, T Patton
- Compton’s encyclopaedia CD-ROM
- Pears cyclopaedia
- Health psychology, S Taylor
- The Human Body, Dr T Smith
- Grey’s anatomy
- DK family encyclopaedia
- Foods that harm foods that heal, Readers Digest