There is and inbuilt biological mechanism for identifying and destroying pathogens within a larger organism,which we term it as Immune system. The immune system is the body's natural defense in combating organisms. The immune defense system has a huge reach to every parts of the body from organs, tissues, cells to protein substances that work together to defend the body against attacks by "foreign" invaders or Pathogens: agents that cause disease. These invaders, called foreign antigens can be in the form of bacteria, virus, fungi, parasites or even single proteins. Fate of the foreign antigen depends on how strong ones immune system is .When infections or the invasion of the foreign particles invades our immune defense medical intervention will be necessary.
Our immune system is responsible for preventing the infection although we are always in contact with one or the other pathogen. Innate immune response and adaptive immune reponse are the back bone of the compact immune system. The former acts as the first line of defense against pathogens while the later is responsible for the second line of defense and also afford protection against re-exposure to the same pathogen in the mere future. The components of the innate immune system include barriers like skin and the internal epithelial layers. These mechanical barriers are assisted with secretions namely the sweat enzymes, low pH environment which favors lyses of the bacterial cell. Although few of the microorganisms are pathogenic to us, there are few beneficiary ones. We having a huge collection of microorganism in our body which prevents pathogens from colonizing in their environment as in our body. But once the barrier has been crossed by cuts or wounds innate immune system responds thru humoral factors which sends signals and activates other mechanisms of defense as the compliment system, coagulation system. Once there is redness, inflammation seen at the are cut it is certain that the body has woke up and is defending itself from the pathogen. Some of the specialized cell which are involved in the innate immune response are macrophages, Neutrophils, Eosinophils, natural killer cells which ingest the pathogen by phagocytosis and destroy it.
There is a connection between the innate immune response and adaptive immune response through molecules namely cytokinins. One of the other important characteristic feature exhibited by our immune response is to differentiate between sel and non self particle is attributed to the adaptive immune response.The major components of adaptive immune response include B-cells and T-cells. Cells which produces antibodies are B-cells and are derived from bone marrow. Antibodies have antigen binding site and binds to virus and prevents further spread of the infection. T-cells matures in thymus and is involved in eliminating virus infected cell and maturation of lymphocytes in turn contributing to innate immune response. T cells attacks the viral infected cell and destroys it completely. Both B cells and T cells not only eliminate the pathogen but also leave behind the memory cell which is responsible for success of most of the immunization procedures.
There are certain disease which leads to immune deficiency as in the case of SCID , Severe Combine Immune Deficiency. This particular disease is due to absence of T cells and in turn B cell function. This disease can be inherited as X linked SCID,Adenosedeaminase deficiency,Omen syndrome, lymphocyte syndrome due to various mutation in several genes .Unless these defects are corrected the child will die of opportunistic infections at an early age.
Gene therapy is one of the major hope to treat patients suffering with SCID, since life outside the sterile environment is almost impossible for them. In gene therapy a normal gene is inserted into the genome to replace an abnormal, disease-causing gene. A carrier molecule called a vector be used to deliver the therapeutic gene to the patient's target cells. Currently, the most common vector is a virus that has been genetically altered to carry normal human DNA. Viruses have evolved a way of encapsulating and delivering their genes to human cells in a pathogenic manner.The first approved gene therapy trials involved children with severe combined immunodeficiency disease, or SCID (Immunodeficiency Diseases), was conducted in 1990s . The missing gene is introduced into a harmless virus, then mixed with progenitor cells from the patient's bone marrow. When the virus splices its genes into those of the bone marrow cells, it simultaneously inserts the gene for the missing enzyme. Injected back into the patient, the treated marrow cells produce the missing enzyme and revitalize the immune defenses, but the success did not remain for longer time and it had been observed that the inserted gene actually caused the expression of an oncogene and hence patients suffered from cancer.Subsequent research is going on to overcome this effect. Hence studies targeting the immune system is critical to advance in medical field through biotechnology.
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