IMMUNITY

Immunity

        The capacity to recognize the intrusion of any material foreign to the body and to mobilize cells and cell products to help remove the particular sort of foreign material with greater speed and effectiveness ‘’is called immunity.

         In animals in addition to physical barriers (skin + mucous membranes) and phagocytes. There is third mechanism, to defend their bodies against the foreign invaders: this is the immune system.

        The components of immune system include the lymphocytes (B and T) and the antibodies are immunoglobulin which are synthesized by vertebrate, in response to antigens: and immobilise it, or sets in motion events that ultimately cause its destruction. Antigen or immunogen is a foreign substance, often a protein which stimulates the formation of antibodies. Antibodies  are specific i.e. cause the destruction of the antigen, which stimulated their production. Antibodies are manufactured in B lymphocytes, then secreted into the lymph and blood where circulate freely.

                T-cells recognize antigen, then combat micro-organism and or effect the rejection of foreign tissues (in case of tissue transparent). This is called cell-mediated response.

  

                B-cells recognize antigen and form plasma cell clone. These plasma cells synthesise and liberate antibodies into the blood plasma and tissues fluid. Here antibodies attach to the surface of bacteria and speed up their phagocytosis, or combine with and neutralise toxins produced by micro-organism, by producing antitoxins. This is called humoral immune response.

          When we get vaccination, against a specific disease (antigen), we become immune to that infection or disease . if we get vaccination against, polio, smallpox, measles, mumps etc., once in our life time , we are protected or become immune to that infection in our future life.

Types of immunity

Active immunity : The use of vaccines, which stimulates the production of antibodies in the body, and making a person immune against the disease or infection, is called active immunity. but this active immunity has been achieved by artificially introducing, antigens in the body, so it is called artificially induced active immunity.

    But when a person is exposed to so infection (antigens) becomes ill and in most cases survives then this immunity, developed against that disease is called naturally induced immunity or auto immune response.

Passive immunity : in contract to active immunity, in which case antigens are introduced to stimulate the production of antibodies, but artificial or natural method; antibodies are injected in the form of antisera, to make a person immune against a disease. This is called passive immunity.

The method of passive immunization is used to combat active infections of, tetanus, infection hepatitis, rabies passive immunity is produced by the antitoxins so the serum is called antivenom serum.