Vaccination & True Immunity Pages 916-919

Memory Cells T cells activate B cells B cells go through cell divisions Cell cloning  through mitosis Produce the same antibody There are two types of cloned B cells Antibody secreting plasma cells Secrete antibodies immediately Fight off first infections Memory cells Do not secrete antibodies during the first infection Long lived & remain in blood stream waiting for a secondary infection

Fundamental Principles of Immunity Apply for all types of infection Challenge and Response Immune system must be challenged by an antigen during first infection to develop immunity Macrophages, T cells, B cells Clonal selection Particular B cells & multiple divisions Memory Cells Provide long term immunity You must experience a pathogen (antigen) to produces these cells

Active and Passive Immunity The event just described represent active immunity Active immunity always  memory cells  long term immunity Passive Immunity When one organisms acquire antibodies which were produced in another organism Only the organism which produced the antibodies has the memory cells Acquiring antibodies = only short term benefit

Examples of Passive Immunity Transfer of antibodies from mother to fetus through the placenta Memory cell are not transferred Breast milk (colostrum) High antibody concentration Injection of antibodies Antivenoms produced for treatment of poisonous snake and spider bites

Immunity may be natural or artificial Acquired from mother; immunity from infection Artificial: Due to inoculation from vaccine

Vaccines and Immunity You must be exposed to a specific pathogen in order to become immune to it For many diseases, scientists have developed vaccines that act as the first exposure to the pathogen

How are vaccines produced? Several methods: Select a particular “weak” strain of the pathogen Heat the pathogen Chemical treatment of the pathogen The leukocytes responsible will recognize the weakened pathogen & primary immune response will take place Includes formation of memory cells

More on vaccines Vaccines do not prevent an infection, but, when exposed to the real pathogen, secondary immune response is quicker than primary After vaccination, most people respond so quickly to the real pathogen that only very mild symptoms (or no symptoms) result

Graph of antibody production in the primary and secondary Immune response Secondary immune response produces more antibodies in less time Second exposure to same antigen First exposure to antigen Primary immune response

Turn and talk What are the benefits and dangers of vaccines? Why do many nations, including the U.S., require vaccines?

Benefits and Dangers Most people agree vaccination has benefited humankind Some diseases, like smallpox, have been eliminated (no reported case since 1977) Result of WHO smallpox vaccination program However, not all are happy … Being forced by a governmental agency Individual right to make decisions about their health

Benefits Possible total elimination of the disease Seen with smallpox; possible with polio & measles? Decrease spread of epidemics and pandemics Implications of increased international travel Preventative medicine is typically more cost-effective Vaccine is cheaper than treating the disease Vaccinated individual benefits b/c the full symptoms of the disease do not have to be experienced to gain immunity.

Danger Prior to 1999, many vaccines contained thimerosal, a mercury-based preservative Mercury: neurotoxin; infants & young children susceptible Perception exists that multiple vaccines given to children in a short time frame may “overload” their immune system Anecdotal evidence that MMR vaccine link to autism Measles, mumps, rubella Hot issues topic In some cases, vaccines lead to allergic reactions

Practice #1 Which type of cell is responsible for secondary immune responses to a pathogen? A. Cytotoxic T-cells B. Phagocytes C. Macrophages D. Memory cells

Practice #2 Some infectious diseases are treated by injecting the patient with antibodies after they have been exposed to the disease. What type of immunity is this? A. Artificial and active B. Artificial and passive C. Natural and passive D. Natural and active

Practice #3 Which is not true of active immunity? A. It can be produced by exposure to a disease causing organism. B. It can be produced artificially. C. It can be produced by a virus. D. It can be transferred via the colostrum.

#4 Which curve shows the response of the immune system to a vaccine, followed by an infection?