Immunology | Immune system| Immunity

                   
                Specific defence mechanism is not present from the birth but is acquired during one's own life span.It is develpoed by an organism in response to a disease caused by the infection of microbes or vaccines.It is due to the presence of an extremely powerful specific immune system which forms third line of defence.The most  peculiar characteristics of immune system is thst it can be differentiate between self(body's own cells) and "non-self"(foreign).It provides defence against invading agents such as lethal bacteria,viruses,toxins and even transplants.In this,protective lymphocytes of the body produce antibodies which not only inactivate the antigens and relieve from an infectious disease but also provide immunity against further attack.

specific defence mechanism

                    The antigenic specificity of the immune system permits it to distinguish subtle differences among antigens.Antibodies can only distinguish between two protein molecules that differ in only a single amino acid.The immune system is capable of generating tremendous diversity in its recognition molecules,allowing it to recognize billions of unique structures on foreign antigens.Once the immune system has recognized and responded to an antigen,it exhibits immunologic memory;that is a second encounter with the same antigen induces a hightened state of immune reactivity.Finally, the immune system normally responds only to foreign antigens,indicating that is capable of self/nonself recognition. 

                  The phagocytic cells crucial to nonspecific immune responses are intimately involved in activating the specific immune response.Conversely,various soluble factors produced by a specific immune response have been shown to augment the activity of these phagocyticcells.As an inflammatory response develpos,for example, soluble mediators are produced that attract cells of the immune system.The immune response will,in turn,serve to regulate the intensity of teh inflammatory response.Through the carefully regulated interplay of adaptive and innate immunity,the two systems work together to eliminate a foreign invader.