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Wednesday, 27 July 2016


Our bodies are protected from germs or disease causing organisms in many ways. Some of the ways arise from the body's own defence mechanism others are man-made. Here, we shall be concerned mainly with the man made methods. For instance animals which carry disease are exterminated; e.g. rats, fleas, mosquitoes, etc. Infected individuals are isolated until they are no longer infectious. Germs are destroyed by sterilization and also using disinfectants.

By the use of sunsisipticran the slab for instance when the skin is cut, a door is opened to disease causing organisms and the cut may go septic. However, this can be prevented by applying a substance which kills germs, such substance called antiseptics (e.g. iodine). By using antitiotics to treat bacthia. Others are drugs are made from chemical laboratories to kill micro-organisms.

The other man~made ways of protecting the body against microorganism are Immunization vaccination and inoculation

When a particular form gets into the blood stream. it usually causes you to produce antibodies which kill the microorganisms)(germs). Now suppose a smail amount of fluid obtained from some dead germs of some kind is iniected into your blood before you have a disease caused by that germ. What effect Will this have? The fluid contains antigens so it causes you to make and bodies you will then be protected aganllt the disease.

This is what doctors do to make people immuned to various diseases. The process is called immunisation. The first person to immunize someone against a disease was the English physian Edward ienner. in 1796, he immunised a young boy against the dreaded disease. small pox. He did this by giving him serum from a girl who had a related disease called Cow Pox or Vaccine. For this reason the process of being immunized is called vaccination. The material which is injected into the blood stream is called the vaccine. Jenner used pus from the girl's spots as his vaccine and he scratched it into the boys sking with a thorn. Since Jenner’s day immunization has been extended to many other diseases; both viral and bacterial.

When a doctor immunizes you, he puts a small quantity of vaccine into your bloodsteam. This is called inoculation.

Normally it is done with a hypodermic needle or by scratching the skin; though in some cases the vaccine can be taken my mouth. The vaccine itself is made fromgerms which are dead or at least inactive. The germs must be in this state otherwise they might give you the disease the doctor is trying to protect you from. Note that the body reacts to the presence of any strange or foreign protein in the blood in illuding those of micro-organisms by producing antibodies.

The antibodies neutralize the protein called antigen and help prevent it (protein) from doing ham or destroying it.

Antibodies normally persist in the body for a time after a person has recovered from a disease and give him protection from that disease (though not from others). This protection is called immunity and may be for a few weeks (cholera) or for life eg. Small pox; depending on the disease.

Child immunization

Note that for diseases like cholera, polio and typhoid, immunization protects you for only a limited time and you need to be given further doses of vaccine from time to time to keep up our protection in order to maintain the levels of a particular antibody in the blood. These are called boosters.

Immunity is the ability of the body to resist attack by a disease it has previously suffered from by producing antibodies. For example when a person is attacked by a particular disease for the first time the signs and symptoms characteristic of that particular . disease appear.

Meanwhile the presence of that particular pathogen (micro-organism) in the body causing the disease stimulate the production of specific antibodies by the white blood cells (lymphocytes) to destroy the particular pathogen and the person recovers. Upon a second invasion of the same pathogen the lymphocytes of the body quickly recognise the pathogen and rapidly produce more antibodies to destroy the invading pathogen so that the signs and symptoms do not appear the second time. The person is said to be immuned against that particular disease.

All forms of immunity developed during an individual's lifetime is said to be acquired. The acquired immunity is either natural or anihcial.

Natural Acquired Immunity: This is the immune state produced by natural means. This can further be divided into two; which are active natural acquired immunity and passive natural acquired immunity.

a. Active natural acquired immunity This is acquired by the production of antibodies by the individual’s own white blood cells (lymphocytes) during some infection. For instance when a person is attacked by a disease caused by microorganisms or recovers from a disease, the person retains the ability to produce antibodies more rapidy to attack the same micro-organism which may invade the body in future. As a result the disease will not
occur again and he is said to be immuned against the disease.

This is called active naturally acquired immunity since the actual microorganism stimulates the production of the antibody.

b. Passive natural acquired immunity This is acquired when ready made antibodies are transferred naturally to an individual, for instance, a foetus receives ready-made antibodies from the mother through the placenta and through the breast milk. The body is thus immune to those diseases for which the mother transferred the ready-made antibodies. The baby gradually excretes these received antibodies and the level of the antibodies decreases to give continous immunity. This is because the already made antibodies from the mother does not induce the baby's natural system (lymphocytes) to produce antibodies and so this kind of immunity is termed passive. It is very helpful for the bady against certain kinds of diseases for the first few weeks in his life.

This is the immune state developed by the injection of a vaccine (i.e antigen) into the body through the process of immunization.

This can further be divided into two; which are active artificial acquired immunity and passive artificial acquired immunity.

a. Active artificial acquired immunity

This is the immune state developed by the injection of a vaccine into the body and the body reacting by producing its own antibodies against that specific vaccine or antigen. Whether the body becomes immune depends on sufiicient concentration of antibody in the blood stream. With some vaccinations the amount of antibody produced after the first injection is too low to provide immunity and a second booster injection has to be given.

The body reacts more vigorously by producing more antibodies to destroy the invading pathogen.

b. Passive artificial acquired immunity This is the immunized state developed when antibodies in a serum are injected into an individual. it is possible for older people to acquire passive immunity by receiving an injection of serum containing ready-made antibodies. For example. if a farmer gets soil or animal faeces into a deep wound. there is no point in giving an injection of live attenuated tetanus bacteria. The body may already be trying to combat active live germs but an injection of a serum containing the antibodies against tetanus will give instant protection.

In summary, there are four types of acquired immunity, which are active natural acquired, passive natural acquired, active artificial acquired and passive artificial acquired.

 immunization is the process of introducing vaccine into an animal or a person as to confer immunity on the individual against the occurrence of a particular disease in the future. The basis is that the antigens from the dead or the inactivated micro-organism in the vaccine may cause a mild form of the disease but more importantly stimulate the lymphocytes rapidly to produce antibodies in the body for the future. So that when in the future the active form of the same pathogenic micro-organlsm invades the body of the immunized person, antibodies are quickly raised against it.
The active and harmful micro-organism is destroyed and the disease does not occur. Practical example of importance of immunization is the vaccination against the six childhood killer diseases namely diphtheria, tetanus, whooping cough, poliomyelitis, tuberculosis and measles. Children, especiaily, are always immunized against these so as to prevent a catastrophe when they are infected with the respective micro-organisms in short, immunization prevents people from manifesting the characteristics of a disease since the micro-organism causing the disease are destroyed by the produced antibodies in the immunized person. Thus in an outbreak of a disease the immunized person against that particular disease is not affected. This can lead to increase in productivity and a healthy life.

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