Active vs Passive Immunity – Definition and Differences


Active vs Passive Immunity
Active immunity occurs when you make antibodies, while passive immunity is when you are given antibodies.

Active and passive immunity are two fundamental types of immune responses that our bodies use to fight off diseases and infections. Here’s a detailed exploration of each:

Active Immunity

Definition

Active immunity occurs when the body’s immune system produces its own antibodies in response to the presence of a pathogen or a vaccine. This type of immunity is typically long-lasting, sometimes lifelong.

Types

There are two broad types of active immunity:

  1. Naturally Acquired Active Immunity: This happens when a person is exposed to a live pathogen, develops the disease, and then recovers, creating a memory in the immune system. For example, someone who recovers from chickenpox typically develops a natural immunity to future infections of the same virus.
  2. Artificially Acquired Active Immunity: This form is the result of a vaccine, which introduces a weakened or dead pathogen or a part of it (like a protein) into the body. Vaccines for diseases like polio and measles work this way, prompting the immune system to respond and build immunity without causing the actual disease.

Advantages

  • Active immunity provides long-term, often lifelong protection.
  • Memory cells formed during the immune response quickly respond to future exposures.

Disadvantages

  • This type of immunity takes time to develop after initial exposure to the antigen.
  • Natural infections are sometimes severe or even lethal.
  • Vaccines sometimes cause mild symptoms or reactions.

Passive Immunity

Definition

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.

Types

Here too, there are natural and artificial routes:

  1. Naturally Acquired Passive Immunity: This occurs in newborns who receive antibodies through the placenta during pregnancy or from breast milk after birth. These antibodies provide immediate, short-term protection.
  2. Artificially Acquired Passive Immunity: This involves the introduction of antibodies from an external source, like in the form of immune globulin treatments. For example, this method occurs in the treatment of rabies or snake bites, where immediate protection is necessary.

Advantages

  • Unlike the delayed response by active immunity, passive immunity provides immediate protection.
  • This is useful in emergency situations where immediate immunity is needed.

Disadvantages

  • Passive immunity is short-lived, as the body does not produce memory cells.
  • The introduction of antibodies sometimes produces side effects, including allergic reactions, anaphylaxis, or serum sickness, which is a delayed allergic reaction in response to foreign proteins.
  • Some monoclonal antibodies affect normal immune system function, potentially increasing susceptibility to infections.

Comparison of Active and Passive Immunity

Both active and passive immunity play crucial roles in our body’s defense against diseases. Vaccines, which utilize active immunity, are instrumental in controlling and even eradicating certain diseases. On the other hand, passive immunity is a lifesaver in urgent situations.

Combining Active and Passive Immunity: Hybrid Approaches

Hybrid immunity approaches involve the simultaneous or sequential use of active and passive immunization strategies. This combines the immediate effectiveness of passive immunity with the long-term protection offered by active immunity.

Applications and Examples

  • Immediate and Long-Term Protection: In some cases, patients exposed to a severe infection or toxin receive passive immunity through antibody treatments for immediate protection, followed by a vaccine to develop active immunity for long-term protection. An example is rabies post-exposure prophylaxis, where patients receive rabies immunoglobulin (passive immunity) along with the rabies vaccine (active immunity).
  • Autoimmune Diseases and Transplant Patients: Individuals with compromised immune systems, such as those with autoimmune diseases or organ transplant recipients, might receive monoclonal antibodies (passive immunity) for immediate defense against infections, alongside immunizations for long-term protection.
  • Cancer Immunotherapy: Some cancer treatments involve a hybrid approach, where passive immunity through monoclonal antibodies targets cancer cells directly, while cancer vaccines (active immunity) stimulate the body’s own immune response against cancer cells.
  • COVID-19 Treatment and Prevention: During the COVID-19 pandemic, some patients received monoclonal antibody treatments for immediate virus neutralization (passive immunity), along with COVID-19 vaccines to build long-term immunity (active immunity).

Advantages

  • Rapid and Sustained Protection: This approach provides immediate protection through passive immunity while the longer-lasting active immunity develops.
  • Enhanced Efficacy: For certain diseases, especially those requiring an immediate response, hybrid approaches enhance treatment efficacy.
  • Flexibility: It allows for tailored treatments, especially in individuals with special medical needs or in unique medical scenarios.

Challenges

  • Coordination of Treatments: Implementing a hybrid approach requires careful planning and timing to ensure both forms of immunity work effectively and safely.
  • Cost and Accessibility: Such treatments are more expensive and logistically complex, potentially limiting their accessibility.
  • Risk of Adverse Reactions: Combining different types of immunological interventions increases the risk of adverse reactions or complications.

References