Immunity - Immunisation is a quick, simple and safe way to protect an individual from infection.

University Degree Medicine and Dentistry

Felicity Collier 12c Health and social unit 3

Immunity

Immunisation is a quick, simple and safe way to protect an individual from infection. The more people immunised in childhood, the more rare diseases become. Immunisation therefore protects not just your child but babies, adults and other children too.

Artificial immunisation is a way of creating immunity to certain infections using relatively harmless antigens that come from, or are similar to, the micro organism that cause infection. Microorganisms can be viruses, such as measles, or bacteria such as Diphtheria.

An antibody is an immunoglobulin (protein molecule produced to combat microbial infection and provide immunity) produced because of an antigen introduced to the body. An antigen is a substance that stimulates an immune response (triggered when the body detects the presence of foreign material, this substance is an antigen) e.g. can be pathogens, vaccines, pollen, and even some food. Each antigen stimulates the production of a specific antibody itself. The antibody helps the body to fight against infection. Antibody production is a major function of the immune system and is carried out by B-lymphocytes; these are a type of white blood cells.

Cells called T-lymphocytes “regulate the immune response by releasing chemicals to stimulate or suppress antibody production” (GNVQ advanced options, Human physiology and health in the caring context). The T-lymphocytes take part in cell killing (cytotoxicity) and inflammation, in the case of AIDS “the virus attacks the T-lymphocyte and the victim cannot then make antibodies effectively” (GNVQ advanced options, Human physiology and health in the caring context). B-lymphocytes work by identifying antigens either as virus or bacterium, they then secrete specific antibodies that bind to antigens (antigen antibody complex) and identify antigen complex to fight the infection. In the serum and lymph, antibodies act on antigens. B-cell produced antibodies may either be attached to B-cell membranes or free in the serum and lymph. A phagocyte (white blood cell with a lobed nucleus) then approaches the enzyme and engulfs it. Once engulfed the microbe is attacked and destroyed. This process happens out in the blood.

There are two types of immunity, active immunity and passive immunity. Active immunity contains an attenuated (weakened) or killed form of the disease-causing organism, or a killed sample if the disease, this is also known as inactivated. Passive immunity saves the body from making its own antibodies, serum from an already immune person is injected into an infected person, and this is not a vaccine.

The vaccine for active immunity is either given by mouth or injection. The given vaccine helps the immune system to produce antibodies that fight against that particular bacterium or virus. Clones of B-lymphocyte memory cells stay in the blood so that if the body comes into contact with the antigen again it will not result in development of the antigen, as the body will have the knowledge of how to fight it. This is called active immunity because the immune system is relied on to produce antibodies. Attenuated (weakened) disease organism vaccines are not given to people with damaged immune systems. Some vaccines require booster treatment; this means that they have to be given more than once following a particular schedule others only require one vaccine.

Differences between active and passive immunity:

Primary and secondary response of antibody production

“The production of antibody, involving circulating monocytes, T and B-lymphocytes and tissue bound macrophages, may result in either a primary and/or secondary response.” ()

After the individual first comes into contact with a particular antigen is the primary response. The body will take 3-14 days after infection until it produces antibodies. The period between infection and the onset of antibody production is the Primary latent period. After this latent period the amount of antibodies in the blood rises rapidly and then begins to fall. Memory cells are produced during the immune response, these are clones of the lymphocytes that fought of the pathogen (micro organism that cause disease) remain in the body. The body now has long term defence against second infection of this antigen.

The secondary response happens if a second infection occurs. A much smaller amount of antigen will induce the secondary response. The body will have a rapid production of antibodies in which more antibodies are produced than before. This is a quick response, which means the pathogen is destroyed before it causes symptoms. A booster vaccination may be needed at a later time.