Immunity is the ability of the body to resist infection by a particular pathogen. It can be classified in two ways.Active or passive?
• Active immunity: the body makes its own antibodies after being exposed to an antigen. Lymphocytes are activated and memory cells form, so immunity is long-lasting, but it takes days to weeks to develop.
• Passive immunity: the body is given ready-made antibodies from another individual. Protection is immediate, but no memory cells are made and the antibodies are gradually broken down, so it lasts only weeks to months.Natural or artificial?
• Natural: happens during normal life.
• Artificial: results from deliberate medical intervention.Combining these gives four types:
• Natural active: catching a disease and making antibodies and memory cells, for example after chickenpox.
• Artificial active: vaccination, where antigens are introduced deliberately.
• Natural passive: antibodies passing from mother to fetus across the placenta, or to the baby in breast milk, especially colostrum.
• Artificial passive: injection of antibodies made by another person or animal, for example tetanus antitoxin.Natural passive immunity protects babies during their first months, before their own immune system has met many antigens. As the mother's antibodies are broken down, babies need vaccinations.A quick way to remember: in active immunity your own lymphocytes do the work and memory cells are made; in passive immunity the antibodies are borrowed.
• Active immunity: the body makes its own antibodies after being exposed to an antigen. Lymphocytes are activated and memory cells form, so immunity is long-lasting, but it takes days to weeks to develop.
• Passive immunity: the body is given ready-made antibodies from another individual. Protection is immediate, but no memory cells are made and the antibodies are gradually broken down, so it lasts only weeks to months.Natural or artificial?
• Natural: happens during normal life.
• Artificial: results from deliberate medical intervention.Combining these gives four types:
• Natural active: catching a disease and making antibodies and memory cells, for example after chickenpox.
• Artificial active: vaccination, where antigens are introduced deliberately.
• Natural passive: antibodies passing from mother to fetus across the placenta, or to the baby in breast milk, especially colostrum.
• Artificial passive: injection of antibodies made by another person or animal, for example tetanus antitoxin.Natural passive immunity protects babies during their first months, before their own immune system has met many antigens. As the mother's antibodies are broken down, babies need vaccinations.A quick way to remember: in active immunity your own lymphocytes do the work and memory cells are made; in passive immunity the antibodies are borrowed.