Which of the following convey the longest lasting immunity to an infectious agent?
a. Naturally acquired passive immunity
b. Artificially acquired passive immunity
c. Naturally acquired active immunity
d. All of these
e. None of these
The correct answer and explanation is :
The correct answer is c. Naturally acquired active immunity.
Explanation:
Immunity refers to the body’s ability to resist or defend itself against infections or harmful substances. There are two primary types of immunity: passive and active. These can be acquired either naturally or artificially, and each type has varying durations of effectiveness.
- Naturally acquired passive immunity:
- This type of immunity occurs when a mother passes antibodies to her baby, either through the placenta (during pregnancy) or through breast milk (after birth). The immunity provided in this way is short-term because the baby’s immune system does not produce its own antibodies. The antibodies from the mother offer temporary protection against infections but do not last long after birth. This is passive because the baby’s immune system is not actively involved in creating these antibodies.
- Duration: Short-term (a few weeks to months).
- Artificially acquired passive immunity:
- This immunity is provided through the administration of antibodies (such as immune globulin) to an individual, often in the form of injections or infusions. This provides immediate but temporary protection against certain diseases. For example, a person exposed to rabies may receive rabies immune globulin for immediate passive immunity. However, the immunity is short-lived because the individual’s body is not making its own antibodies.
- Duration: Short-term (weeks to a few months).
- Naturally acquired active immunity:
- This occurs when an individual is exposed to a pathogen in the environment (e.g., through infection) and the body responds by producing its own antibodies and memory cells. These memory cells “remember” the pathogen, allowing the immune system to recognize and fight the pathogen more effectively if exposed again in the future. This type of immunity can last for years or even a lifetime. Examples include immunity to diseases such as chickenpox or measles after natural infection.
- Duration: Long-term (years to lifetime).
- Artificially acquired active immunity:
- This type of immunity is induced through vaccinations. A vaccine contains components of the pathogen (e.g., inactivated virus or bacterial proteins) that stimulate the immune system to produce antibodies and memory cells without causing disease. This type of immunity can also last for many years, depending on the pathogen and the effectiveness of the vaccine.
Conclusion:
Naturally acquired active immunity is the longest-lasting type of immunity because it involves the production of memory cells by the immune system, which can recognize and respond to pathogens for many years or even a lifetime. This is in contrast to passive immunity, which is short-lived since it does not involve the production of the immune system’s own antibodies.