Active, Passive, Natural and Artificial Immunity

Passive immunity is the introduction of antibodies into an individual.The antibodies will have been produced externally and as soon as the individuals are injected with the antibodies the individual would acquire immunity immediately whereas active immunity takes time (usually several weeks) to develop.However, passive immunity lasts only for a few weeks or months as the antibodies are eventually destroyed. Only active immunity is long-lasting. Examples are anti-snake venom antibodies and the acquired immunity of the fetus when antibodies pass from the mother to the fetus across the placenta.Active immunity is the stimulation of the production of antibodies.Natural active immunity arises by infection.Artificial active immunity involves inducing a response by vaccination without the individual suffering the symptoms.