The evolution of immune system.

It can be defined as a complex evolutionary unit and it can be said that the immune system of primitive organisms is also primitive. The immune system involves numerous elements, which have undergone many evolutionary changes, some which are neutral, some are selected, to form the basis of modified organisms that live among us in the 20th century and whose immune systems have adapted to the damaging environment humans have created in this era. All these different species including, humans themselves, have perhaps evolved beyond their apparent primitive state into something more realistic to survive in today’s world. The immune systems have been modified by factors linked not only to the internal evolution of their elementary genes but also by coevolution with factors in the internal environment, such as cellular constraints, metabolism, mode of reproduction and progeny size. It is significant to learn and understand our immune system because increasing our knowledge in this area could help suggest solutions to clinicians when they are faced with deficiencies and anomalies in the immune system of man.

The outline of innate and adaptive immunity portrays an interactive system that defends the host from transferrable diseases and from cancer. This would not be comprehensive without stating that the resistant of our body can function indecorously. Occasionally the immune system fails to defend the host effectively or misdirects its activities to inflict uneasiness, incapacitating illness, or even death. There are numerous communal appearances of immune dysfunction:

■ Allergy and asthma

■ Graft rejection and graft-versus-host disease

■ Autoimmune disease

■ Immunodeficiency

Allergy and asthma are results of unsuitable immune responses, often to shared antigens such as plant pollen, food, or animal dander. The likelihood that certain substances amplified sensitivity rather than protection was documented in about 1902 by Charles Richet, who attempted to immunize dogs compared to the toxins of a kind of jellyfish, Physalia. He and his associate Paul Portier detected that dogs exposed to sublethal dosages of the toxin reacted almost suddenly, and fatally, to subsequent challenge with tiny amounts of the toxin. Richet decided that a successful injection or vaccination results in phylaxis, or defense, and that an contrary result may occur. Anaphylaxis in which contact to antigen can result in a possibly lethal sensitivity to the antigen if the contact is recurrent. Richet received the Nobel Prize in for his detection of the ana-phylactic response.

Providentially, most allergic reactions in humans are not quickly fatal. A specific allergic or anaphylactic response typically involves one antibody type, named IgE. Binding of IgE to its specific antigen (allergen) releases constituents that cause irritation and swelling. When an allergic individual is exposed to an allergen, signs may include sneezing, wheezing, and struggle in breathing (asthma); dermatitis or skin eruptions (hives); and, in more dangerous cases, asphyxiation due to blockage of airways by swelling. An important fraction of our health resources is used to care for those suffering from allergy and asthma. The occurrence of allergy and asthma in the United States place these grievances among the most shared reasons for a visit to the doctor’s dispensary or to the hospital emergency room.

When the immune system come across foreign cells or tissue, it responds sturdily to rid the host of the invaders. Nevertheless, in some cases, the transplantation of cells or an organ from additional individual, although observed by the immune system as a foreign assault, may be the only possible action for disease. For instance, it is projected that more than 60,000 persons in the United States alone could profit from a kidney transplant. Since the immune system will attack and reject any relocated organ that it does not identify as self, it is a serious blockade to this possibly life-saving treatment. An added hazard in transplantation is that any relocated cells with immune function may sight the new host as nonself and respond against it. This reaction, which is called graft-versus-host disease, can be lethal. The rejection reaction and graft-versus-host disease can be repressed by drugs, but this kind of treatment overpowers all immune function, so that the host is not threatened by its immune system and develops susceptible to infectious diseases. Transplantation educations have played a main role in the growth of immunology. A Nobel prize was presented to Karl Landsteiner, for the detection of human blood groups, a discovery that permitted blood transfusions to be carried out securely. , G. Snell, J. Dausset, scientists and B. Benacerraf were known for discovery of the major histocompatibility complex, in 1991, E. D. Thomas & J. Murray were prearranged Nobel Prizes for developments in transplantation immunity. To allow a foreign organ to be recognized without overpowering immunity to all antigens remains a test for immunologists today.

In many individuals, the immune system breakdowns by losing its sense of self and nonself, which allows an immune attack upon the host. This disorder, autoimmunity, can root a number of chronic incapacitating diseases. The indications of autoimmunity vary depending on which tissues and organs are under a threat. For instance, multiple sclerosis is caused by autoimmune dysfunction on the brain and CNS, Crohn’s disease affects the tissues of the gut, & rheumatoid arthritis is characterized by its affect on the joints of the arms and legs. The genetic and ecological factors that cause and sustain autoimmune disease are very dynamic areas of immunologic research, as is the hunt for improved treatments.

If any of the many mechanisms of innate or specific immunity is faulty because of genetic irregularity, or if any immune function is lost due to damage by chemical, physical, or biotic agents, the person suffers from immunodeficiency. The austerity of immunodeficiency disease

Allergy and Asthma

Even though the immune system serves to defend the host from infection and cancer, unsuitable responses of this organization can lead to disease. Common amid the consequences of immune dysfunction are allergies and asthma, together they are serious public health problems. Particulars of the mechanisms that cause allergic and asthmatic retorts to environmental antigens. Merely specified, allergic reactions are responses to antigenic impetuses that outcome in immunity based chiefly on the IgE class of immunoglobulin. Contact to the antigen

(or allergen) activates an IgE-mediated release of particles that cause symptoms extending from sneezing and dermatitis to swelling of the lungs in an asthmatic attack. The order of events in an allergic reply is portrayed in the reaction.

The uneasiness from common allergies like plant pollen allergy (ragweed allergy) contains a week or two of whooping and runny nose, which may seem minor compared with health complications such as cancer, cardiac arrest, or life-endangering infections. A grave allergic reaction is asthma.

Allergy and Asthma as Public Health issues a chronic illness of the lungs in which swelling, arbitrated by ecological antigens or infections, causes severe trouble in breathing. Roughly 15 million people in the US have asthma, and it causes about 5000 deaths in a single year. In the past twenty years, the occurrence of asthma in the Western World has folded.


The device by which the huge diversity of B and T cells is generated is a haphazard process that unavoidably gives rise to some receptors that identify the body’s own elements as foreign. Lymphocytes having such self-reactive receptors, though, are eliminated or reduced impotent by numerous diverse mechanisms, so that the immune system does not usually make significant amounts of antibodies or T cells that are sensitive with the body’s mechanisms (self antigens). Yet, an immune response to self, termed autoimmunity, can happen, and some of the conducts that self-directed immune responses reason damage causes Allergies.

Knowing and classifying autoimmune disorders is hard given that all humans have numerous self-reactive antibodies in the blood but most of them show no sign of disease. Subsequently, the credential of autoantibodies is not a adequate diagnostic tool for defining the presence of an autoimmune disorder. There is a modification between an autoimmune response and disease: in the prior case the autoantibodies do not inflict dysfunction, but in the latter they do.


The range of autoimmune disorders is extensive, ranging from those that contain a single organ to others that mark several different organs as a secondary result of the presence of immune complexes in the gesticulation. Some of these autoimmune syndromes are discussed and causes are given. The subsequent disorders have been selected to illustrate some of the very different complications that can arise from autoimmunity.

Hashimoto disease, graves disease are 2 common autoimmune disorders in the thyroid gland

Autoimmune hemolytic anemia resultant from the formation of autoantibodies against the RBCS

Pernicious anemia, autoimmune gastritis occurs when there is a failure to absorb vitamin B12 that is essential for proper maturations of the RBCs

Rheumatoid arthritis is also a chronic swelling that affects connective tissues and the synovial membrane lining the peripheral joints.

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