active and passive immunity and the mechanism of action

active and passive immunity and the mechanism of action

1. Active and Passive immunity Submitted by SAVIDHA SAM MSc II Zoology St.Gregorios college Kottarakkara

2. What is Immunity? Immunity is the ability of the body to defend itself against disease-causing organisms. Everyday our body comes in contact with several pathogens, but only a few results into diseases. The reason is, our body has the ability to release antibodies against these pathogens and protects the body against diseases. This defence mechanism is called immunity. Types of Immunity There are two major types of immunity:

3. ACQUIRED IMMUNITY Acquired immunity or adaptive immunity is the immunity that our body acquires or gains over time . Unlike the innate immunity, this is not present by birth. The ability of the immune system to adapt itself to disease and to generate pathogen-specific immunity is termed as acquired immunity. It is also known as adaptive immunity.

4. Active immunity Active immunity is a type of immunity where the body produces its own antibodies and immune cells in response to exposure to a pathogen or a vaccine. It is part of the adaptive immune system and provides long-lasting or even lifelong protection against specific diseases. Developed by host itself Involves Antibody Production : The immune system detects antigens (foreign substances) and generates antibodies to neutralize them. Immunological Memory : Once the immune system encounters a pathogen, it "remembers" it, allowing for a quicker and stronger response in the future.

5. Natural active immmunity Natural active immunity is a type of immunity that develops when the body is exposed to a pathogen through natural infection. During this process, the immune system recognizes the pathogen, mounts a response, and creates memory cells for future protection. Occurs naturally: acquired through exposure to infectious agents Involves Immunological Memory : The immune system "remembers" the pathogen for faster response in future infections Long-Lasting : Protection often lasts for years or a lifetime, depending on the pathogen.

6. Artificial active immunity

7. vaccination Vaccination is a medical process in which a person is given a vaccine to stimulate their immune system to develop protection (immunity) against a specific disease. It is a form of artificial active immunity . Vaccine composition : Vaccines often contain weakened, inactivated, or parts of a pathogen (such as a virus or bacteria). These components are called antigens and mimic the pathogen, allowing the immune system to recognize and fight it. How vaccines work : The immune system detects the antigens in the vaccine as foreign and mounts a response. This response involves the production of antibodies and memory cells. If the person is later exposed to the actual pathogen, the immune system "remembers" it and responds more quickly and effectively.

8. Types of vaccines

9. Polio vaccine : the immune system is trained to fight the poliovirus without causing the disease. COVID-19 vaccine: vaccines like mrna-based vaccines stimulate immunity against the sars-cov-2 virus. Tetanus toxoid vaccine : provides immunity against the clostridium tetani bacteria. Hepatitis B vaccine : protects against hepatitis B virus infections.

10. Advantages of active immunity Provides long-term protection : immunity lasts for years or even a lifetime. Develops immunological memory : the immune system "remembers" pathogens for faster future responses. Adapts to pathogens : effective against a wide range of infections. Cost-effective : reduces the need for repeated treatments. Sustainable immunity : continues to protect after initial exposure. Prevents severe disease : reduces the severity of infections upon re-exposure. Supports vaccination : forms the basis of vaccine-based disease prevention.

11. Limitations of active immunity Delayed protection : active immunity takes time to develop after exposure to an antigen. Dependency on antigen exposure : immunity only develops if the immune system encounters a pathogen or vaccine. Risk of severe disease : natural active immunity may require enduring a full infection, which can be harmful or fatal. Less effective in immunocompromised individuals : people with weakened immune systems may not develop strong immunity.

12. Passive immunity  occurs when a person is given antibodies rather than producing them through their own immune system. This type of immunity is temporary , as the borrowed antibodies eventually degrade and get removed from the body. It provides immediate protection against infections or toxins. Unlike active immunity, the recipient's immune system does not produce antibodies or memory cells.   Why passive immunity is important? Protects newborns who cannot produce their own antibodies. Essential in emergencies like toxin exposure or severe infections . Provides a solution for individuals with weakened immune systems PASSIVE IMMUNIT Y

13. Characteristics of Passive Immunity

14. TYPES OF PASSIVE IMMUNITY

15. NATURAL PASSIVE IMMUNITY Natural passive immunity occurs when antibodies are transferred from one individual to another through natural processes, without medical intervention. This type of immunity provides immediate but temporary protection against infections Mechanisms of natural passive immunity Maternal antibodies via the placenta: Maternal antibodies are transferred to the fetus through the placenta , providing essential protection against infections during the early stages of life. This process primarily involves the transfer of igG antibodies , which cross the placenta in the third trimester , aided by neonatal fc receptors ( fcrn ) .

16. These antibodies help protect the newborn against pathogens such as bacteria and viruses that the mother has previously encountered. This passive immunity is crucial, as the infant's immune system is not fully developed at birth. The protection lasts for several months, gradually waning as the infant’s own immune system matures and begins to produce its own antibodies.

17. 2. Antibodies in breast milk: Antibodies in breast milk, especially in the early milk called colostrum , play a vital role in protecting newborns from infections. The primary antibody found in breast milk is IgA , which is important for mucosal immunity. When a mother breastfeeds, IgA antibodies are passed to the infant, coating the baby’s gastrointestinal tract, respiratory system, and other mucosal surfaces. This helps prevent the entry of pathogens such as bacteria, viruses, and other harmful microorganisms. Breast milk also contains igG , igM , and other immune cells that provide additional protection. This transfer of antibodies helps protect the infant from infections, especially in the first few months, before the baby’s own immune system becomes fully functional. The protection provided by breast milk is temporary, but it is crucial for the infant’s immune defense during the early stages of life

18. Features of natural passive immunity Immunity immediate protection : the baby’s immune system is not yet fully developed, so maternal antibodies play a vital role in defense. Temporary immunity : this immunity typically lasts a few months, until the baby’s immune system matures and starts producing its own antibodies. No memory formation : since the baby’s immune system does not actively produce these antibodies, no immunological memory is formed.

19. Artificial passive immunity Artificial passive immunization is normally administered by injection. It is used if there has been a recent outbreak of a particular disease or as an emergency treatment It is induced in an individual by administering preformed antibodies, in form of antiserum , raised against an infecting agent The antibodies can be produced in animals, called “ serum therapy ,” although there is a high chance of anaphylactic shock because of immunity against animal serum itself. Therefore, humanized antibodies produced in vitro by cell culture are used instead, when and if available.

20. Administration of these antisera makes large amounts of antibodies available in the recipient host to neutralize the action of toxins. The preformed antibodies against rabies and hepatitis A and B viruses , etc. Given during the incubation period prevent replication of the virus, and hence alter the course of infection.   The immediate availability of a large number of antibodies is the main advantage of passive immunity.   However, the short lifespan of these antibodies and the possibility of hypersensitivity reaction, if antibodies prepared in other animal species are given to individuals who are hypersensitive to these animals’ globulins (e.G., Serum sickness), are the two noted disadvantages of passive immunity.

21. Mechanism of artificial passive immunity Antiserum or antibody injections: A ntiserum and antibody injections are both used in artificial passive immunity to provide . Antiserum Antiserum is a solution that contains antibodies collected from the blood of animals (such as horses or goats) or humans who have been exposed to or immunized against a specific pathogen or toxin. antiserum is injected into a person who needs immediate protection against a disease. The antibodies in the antiserum bind to and neutralize the pathogen or toxin. This provides immediate but temporary protection since the person’s immune system does not produce these antibodies themselves. Examples: Tetanus antiserum : given after a potential exposure to tetanus bacteria. Rabies antiserum : administered after a potential exposure to rabies, along with the rabies vaccine .

22. 2. Monoclonal antibody injections Monoclonal antibodies (mabs) are lab-made antibodies that are engineered to target specific antigens (usually on pathogens or cancer cells). these antibodies are injected into the body to target and neutralize specific pathogens or cancer cells. Like antiserum, monoclonal antibody injections offer immediate protection , but the immunity is temporary since the body does not produce these antibodies. Examples: Monoclonal antibodies for COVID-19 : these were used to treat COVID-19 patients by neutralizing the virus. Cancer treatments : certain monoclonal antibodies are used to target and treat cancer by binding to cancer cell markers

23. Examples of Passive Artificial Immunity Products 1 . Immunoglobulin products Hepatitis B immunoglobulin (HBIG) : Rabies immunoglobulin (rig) : Tetanus immunoglobulin (tig) : Varicella-zoster immunoglobulin ( vzig ) : 2.. Antitoxins Iphtheria antitoxin : Tetanus antitoxin : 3 . Antivenoms (antivenins) Snake antivenoms : Scorpion and spider antivenoms : 4. Monoclonal antibodies Palivizumab : Monoclonal antibodies for covid-19

24. Advantages of passive immunity It provides immediate protection against infections or toxins. It is life-saving in emergencies, such as snake bites, rabies exposure, or tetanus infection. It protects immunocompromised individuals who cannot produce their own antibodies. It offers early protection to newborns through maternal antibodies. It is useful during outbreaks to provide rapid immunity, especially for high-risk groups. It serves as a temporary alternative for those who cannot be vaccinated. It neutralizes toxin s or venom quickly, preventing severe complications. It does not require the recipient’s immune system to be functional.

25. Limitations of passive immunity It provides only temporary protection lasting a few weeks to months. It does not create immunological memory for future protection. It may cause allergic reactions or serum sickness in some individuals. It does not offer long-term or lifelong immunity. It relies entirely on external source s of antibodies. It is expensive to produce and administer. Some products, like antivenoms, may not be readily available in all regions

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