Main Difference – Active vs Passive Immunity
The immune system protects the body from a variety of pathogens and toxins. Innate immunity provides the first line defense against pathogens through physical and chemical barriers such as skin, mucus layers, and saliva. The second line defense is also generated by innate immunity through phagocytes. The third line defense is generated by adaptive immunity. Active and passive immunity are two types of adaptive immunity. Both active and passive immunity deal with antibodies. The main difference between active and passive immunity is that active immunity is developed by the production of antibodies by person’s own body whereas passive immunity is developed by the antibodies which are produced outside.
Key Areas Covered
1. What is Active Immunity
– Definition, Features, Types
2. What is Passive Immunity
– Definition, Features, Types
3. What are the Similarities Between Active and Passive Immunity
– Outline of Common Features
4. What is the Difference Between Active and Passive Immunity
– Comparison of Key Differences
Key Terms: Adaptive Immunity, Antibodies, Antigens, Artificially-Acquired Active Immunity, Artificially-Acquired Passive Immunity, Naturally-Acquired Active Immunity, Artificially-Acquired Passive Immunity
What is Active Immunity
Active immunity refers to an immunity which results from the production of antibodies by the person’s own immune system in response to a direct contact of an antigen. The two types of active immunity are naturally-acquired active immunity and artificially-acquired active immunity. In naturally-acquired active immunity, the body is naturally exposed to antigens. The surface molecules of the antigen serve as epitopes for the production of antibodies. T cells (cytotoxic T cells and helper T cells), antigen-presenting cells (dendritic cells and macrophages), and B cells (memory B cells and plasma B cells) are involved in naturally-acquired active immunity. Since the immune system of the body produces the antibody by itself, it takes time to acquire naturally-acquired active immunity.
Figure 1: Active Immunity
During artificially-acquired active immunity, the antigens are artificially introduced into the body in the form of vaccines. The immune response to the first exposure to the pathogen is called the primary response. The secondary response occurs at the second exposure to the pathogen, and it generates a much stronger immune response. Due to the production of memory cells, active immunity lasts a long time.
What is Passive Immunity
Passive immunity refers to a short-term immunity, which results from the introduction of antibodies from the outside. Thereby, passive immunity does not require s direct exposure of the body to the pathogens. Since antibodies are introduced into the body, the immune response can be generated rapidly. But, passive immunity only lasts for several days. The different mechanisms of acquiring immunity are shown in figure 2.
Figure 2: Acquisition of Immunity
Passive immunity can be two types; naturally-acquired passive immunity or artificially-acquired passive immunity. Naturally-acquired passive immunity is the transmission of antibodies from mother to the child through colostrum and breast milk. Artificially-acquired passive immunity is the injection of antisera and the injection of snake antivenom.
Similarities Between Active and Passive Immunity
- Both active and passive immunity are two types of adaptive immunity.
- Both active and passive immunity deal with antibodies.
- Both active and passive immunity can be either naturally-acquired or artificially-acquired.
Difference Between Active and Passive Immunity
Definition
Active Immunity: Active immunity refers to immunity, which results from the production of antibodies by the person’s own immune system in response to a direct contact of an antigen.
Passive Immunity: Passive immunity refers to a short-term immunity which results from the introduction of antibodies from the outside.
Antibodies
Active Immunity: Active immunity is mediated by the antibodies produced by the person’s own cells.
Passive Immunity: Passive immunity is mediated by the antibodies produced outside the body.
Pathogen
Active Immunity: The pathogen has direct contact with the body.
Passive Immunity: The pathogen has no direct contact with the body.
Response Time
Active Immunity: Active immunity does not generate a rapid response.
Passive Immunity: Passive immunity generates a rapid response.
Last for
Active Immunity: Active immunity may last for a long time (lifelong).
Passive Immunity: Passive immunity may not last for a long time (2 to 3 days).
Immunological Memory
Active Immunity: Active immunity generates an immunological memory.
Passive Immunity: Passive immunity does not generate an immunological memory.
Side Effects
Active Immunity: Side effects of the adaptive immunity are very low.
Passive Immunity: The body may react to antisera.
In Immunodeficient Hosts
Active Immunity: Active immunity does not work in immunodeficient hosts.
Passive Immunity: Passive immunity works in immunodeficient hosts.
Conclusion
Active and passive immunity are two types of immunities in the antibody-mediated immunity. Active immunity is mediated by antibodies produced by the person’s own body. Passive immunity is mediated by the antibodies produced outside. Passive immunity can be used to generate a rapid immune response. The main difference between active and passive immunity is the origin of antibodies used in each type of immunities.
Reference:
1.“Active Immunity: Definition, Types & Examples.” Study.com, Available here.
2.“Passive Immunization.” History of Vaccines, Available here.
Image Courtesy:
1. “B cell activation” By Fred the Oysteri. – The Immune System (pdf) (Public Domain) via Commons Wikimedia
2. “OSC Microbio 18 05 graph” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia
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