Natural and Artificial immunity

Natural and artificial immunity

1. Natural and Artificial Immunity Atifa Ambreen M. Phil, Microbiology Government College University, Faisalabad

2. Natural Immunity Naturally acquired active immunity occurs when the person is exposed to a live pathogen, develops the disease, and becomes immune as a result of the primary immune response. Once a microbe penetrates the body's skin, mucous membranes, or other primary defenses , it interacts with the immune system. B-cells in the body produce antibodies that help to fight against the invading microbes. The adaptive immune response generated against the pathogen takes days or weeks to develop but may be long lasting , or even lifelong. Wild infection, for example with hepatitis A virus (HAV) and subsequent recovery, gives rise to a natural active immune response usually leading to lifelong protection.

3. Antigen-Antibody Binding Specificity An antibody ( Ab ), also known as an immunoglobulin ( lg ), is a large, Y-shaped protein produced mainly by plasma cells that is used by the immune system to neutralize pathogens such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the pathogen, called an antigen, via the fragment antigen-binding ( Fab ) variable region. Each tip of the "Y" of an antibody contains a paratope (analogous to a lock) that is specific for one particular epitope (similarly, analogous to a key) on an antigen, allowing these two structures to bind together with precision. Depending on the antigen, the binding may impede the biological process causing the disease or may activate macrophages to destroy the foreign substance .

4. Humoral Immunity Humoral immunity is called active when the organism generates its antibodies, and passive when antibodies are transferred between individuals or species. Similarly, cell mediated immunity is active when the organisms' T-cells are stimulated, and passive when T cells come from another organism .