The word immune literally means "free from burden."Used to a general sense,immunity refers to the ability of an organism to regonize and defend itself against infectious agents.Susceptibility,the opposite of immunity,is the vulnerability of the host to harm by infectious agents.Host organisms have many general defenses against invading infectious organisms Immunity produced bu such defenses is called innate immunity.In contrast,adaptive immunity is the ability of a host to mount a defense against particular infectious agents by physiological responses specific to that infectious agent.
Innate immunity,also called genetic immunity,exists because genetically determined characteristics.One kind of innate immunity is species immunity,which is common to all members of a species.For example,all humans have immunity to many infectious agents that cause disease in pet and domestic animals,and animals have similar immunity to some human diseases.Innate immunity also includesthe ability of an organisma to recognize pathogens.(Microbilogy,7th edition by JACQUELYN G. BLACK)
Innate immunity,the body's built-in ability to regonize and destroy pathogens or their products.Innate immunity is largelly a function of phagocytes,cells that can engulf,kill and digest most pathogens.Innate responses recognize a variety of common structural features found on foregion molecules and pathogens,and nearlly all phagocytes have the ability to interact with most pathogens.Interaction in pathogens stimulate large number of phagocytes to activate a number of genes leading to the transcription,translation and expression of proteins that destroy the pathogens.Because many phagocytes are involved,innate immunity developes immediately upon contact with pathogens.
Unfortunately,innate immune responses are not always effective and dangerous infections sometimes occurs.However the phagocytes can activate another defense mechisms called adaptive immunity or specific immunity to...
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