Definition of Passive Immunity
- Passive immunity is resistance to a disease or toxin acquired without the production of antibodies by the immune system.
- Any foreign substance, be it a virus or a poison, is likely to injure the cells of an organism. In order to prevent this, organisms have built both passive and active immunity against common dangers. Passive immunities, unlike active immunity, are present at birth.
- A passive immunity can impede a harmful foreign body in a number of ways. It may be a barrier that stops hazardous substances from entering the organism, or it may be an untrained cell that directly assaults invaders.
- Antibodies can also be transmitted between organisms. This may occur in a variety of natural and manmade methods. Passive immunity in the form of antibodies is transmitted from the mother to the infant via the umbilical cord.
- As the infant’s immune system is weak and still developing, the mother’s antibodies are required to protect the infant against infections until the infant’s immune system is robust enough to provide active immunity to the same diseases.
- There are numerous types of passive immunity, ranging from the barriers that divide the inside of an organism from the outside to the divisions that separate the bloodstream from vital organs, such as the brain.
- Even basic species, such as bacteria, can employ additional passive immunity mechanisms, such as genetic immunities, to protect against antibiotics and other chemical dangers.
Features of Passive Immunity
- Passive immunity is imparted from the outside, therefore exposure to an infectious pathogen or its antigen is not necessary.
- Passive immunity has its effect immediately. It responds immediately to infectious agents.
- Active immunity is more durable than passive immunity. Typically, its effectiveness is limited to a few days.
- Serum sickness is a disease that can arise from exposure to antisera.
Types of Passive Immunity
Passive immunity may be natural or artificial.
1. Natural passive immunity
- During pregnancy, it is observed when IgG is transferred from mother to foetus.
- This is the foundation for preventing neonatal tetanus in newborns through aggressive immunisation of expectant moms.
- It is accomplished by delivering tetanus toxoid to pregnant women during their third trimester.
- This causes the mother to produce large levels of antibodies against tetanus toxin, which are then transferred to the foetus via the placenta.
- After delivery, the antibodies protect newborns against the risk of tetanus.
- During breastfeeding, IgA is also shown to be transferred from the mother to the infant, demonstrating the presence of passive immunity.
2. Artificial passive immunity
- It is caused by administering premade antibodies, typically in the form of antiserum, produced against an infectious pathogen.
- By administering these antisera, enormous quantities of antibodies are made available in the receiver to counteract the effect of poisons.
- During the incubation stage, the administration of premade antibodies against rabies and hepatitis A and B viruses, etc., prevents virus reproduction and thereby modifies the course of infection.
- The fundamental benefit of passive immunity is the immediate availability of huge amounts of antibodies.
- Two downsides of passive immunity are the limited lifespan of these antibodies and the likelihood of hypersensitivity reaction if antibodies generated in other animal species are administered to persons who are hypersensitive to these animal globulins (e.g., serum sickness).
- Combined passive–active immunity is achieved by administering both preformed antibodies (antiserum) and a vaccination to provide both rapid and long-term protection against a disease, respectively.
- This method is used to prevent some infectious diseases, including tetanus, rabies, and hepatitis B.
Advantages of Passive Immunity
- The immune response of passive immunity is “faster than a vaccination” and can provide immunity to a person who does not “respond to immunisation,” typically within hours or days.
- In addition to giving passive immunity, nursing provides significant long-lasting health benefits for the infant, including a reduced incidence of allergies and obesity.
- In contrast to active immunity, which can take days or weeks to develop, passively injected antibodies can provide rapid and immediate protection, such as against bioterrorism chemicals.
- In contrast to vaccination, which depends on the host’s ability to develop an immunological response, passive antibody confers protective immunity regardless of the recipient’s immune condition. Passive immunisation may therefore be the treatment of choice in highly endemic regions where vaccine responses may be suboptimal, in certain patient groups such as hospitalised patients or those suffering from malnutrition and immunodeficiency, or in those who are contraindicated for vaccination.
Disadvantages of Passive Immunity
- Producing antibodies in the laboratory is difficult and expensive, which is a disadvantage of passive immunity. For the production of antibodies against infectious diseases, maybe thousands of human blood donors are required, alternatively the blood of immune animals would be used.
- Patients who are immunised with animal antibodies may experience serum sickness and severe allergic reactions as a result of the animal’s proteins.
- Antibody therapies can be time-consuming and are administered via intravenous injection or IV, whereas vaccinations are less time-consuming and carry a lower risk of complications.
- However, the protection provided by passive vaccination is temporary and may require repeated dosing.
- In addition, when antibodies are administered at the mucosal surface, such as through oral administration, they may be destroyed by gastric acid and proteolytic enzymes. Large-scale production and purification of antibodies might incur considerable costs.
- The generation of variations that lack the determinant that the antibody identifies, such as viral escape mutants, is another downside of mAbs.
Examples of Passive Immunity
Skin as a Passive Immunity
- The skin is a vital component of passive immunity in the majority of mammals. The skin is an organ composed of numerous layers of elongated cells.
- These epidermal cells develop intercellular connections and create a nearly impermeable covering. In reality, it is extremely rare that a virus or bacteria could ever penetrate healthy, unbroken skin.
- The issue is that viruses, bacteria, and numerous poisons are tiny. It only takes a minuscule skin tear for millions of viruses and bacteria to penetrate.
- Active immunities must be created to battle the reproduction of viruses and bacteria and the spread of toxins in the event of a failure of passive immunity.
- While the skin has its drawbacks, it is important in shielding the body from the daily barrage of environmental threats it is exposed to.
- Without skin, you may absorb pollutants and disease straight from the air, water, and soil you contact.
- Simply by separating your internal cells from these threats, a barrier is created, offering passive immunity against a number of potentially dangerous foreign materials.
- However, if a substantial quantity of a toxin penetrates your skin, you could be in danger. Passive immunity is designed to prevent a disease or toxin from entering the body, whereas active immunity can create resistance to a disease after an initial infection. How can you survive if a high amount of toxin is able to penetrate your passive immunity?
Antivenom as a Passive Immunity
- If bitten by a rattlesnake, there is a possibility that you will be injected with the snake’s venom.
- The venom of a rattlesnake is hemotoxic, which means it kills your tissues and prevents your blood from clotting, leading you to bleed to death.
- Given sufficient exposure to little amounts of rattlesnake venom, your body would develop the ability to generate antibodies, allowing you to survive small doses of the venom. In a rattlesnake bite, however, enormous quantities of venom are pumped into the wound.
- Anti-venom administration would be your best chance of life in this situation. These serums include a high concentration of venom antibodies or proteins that attach to the venom and remove it from the bloodstream and tissues.
- Thus, the enormous amount of venom supplied to your system might be neutralised by a single shot or multiple ones.
- Unfortunately, the production of antivenoms is prohibitively expensive due to the fact that the antibodies are often produced in living animals and collected for use in humans.
Passive Immunity in Bacteria
- It has been demonstrated that certain bacteria can incorporate foreign DNA into their own systems.
- In doing so, they frequently obtain an advantage over other bacteria, allowing them to proliferate more.
- Antibiotics pose a danger to germs. Antibiotics function in many ways to destroy bacterial DNA or starve bacteria of nourishment.
- If a single microbe can generate a mutation that renders it resistant to an antibiotic, it will be able to multiply rapidly.
- As these bacteria die, they leave behind fragments of the DNA that enabled them to survive. Sometimes, other bacteria are able to incorporate these DNA fragments into their own DNA, giving them the ability to resist the antibiotic.
- Thus, they are provided with a new passive immunity to the medicine, similar to how infants develop immunity to sickness.
References
- Marcotte H, Hammarström L. Passive Immunization: Toward Magic Bullets. Mucosal Immunology. 2015:1403–34. doi: 10.1016/B978-0-12-415847-4.00071-9. Epub 2015 Mar 13. PMCID: PMC7150278.
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