Problem 14 - Biology E/M

Question

Which is an example of passive immunity? (A) Lifelong immunity. (B) Babies who are nursing receive antibodies from their mothers. (C) You become resistant to a viral infection once you have recovered from it. (D) You become resistant to mumps after receiving the mumps (E) People who have AIDS have antibodies against the virus but are still gravely ill.

Step-by-Step Solution

Answer

(B) Babies who are nursing receive antibodies from their mothers.

Step 1: Understand Passive Immunity

Passive immunity is when antibodies are transferred from one individual to another, providing temporary protection against infectious agents. It is not acquired by direct exposure to the antigen and does not involve the immune system actively producing antibodies.

Step 2: Evaluate Each Option

- (A) Lifelong immunity: This is typically an example of active immunity, where the body has developed its own antibodies against a pathogen. - (B) Babies who are nursing receive antibodies from their mothers: This involves the transfer of antibodies through breast milk, fitting the definition of passive immunity. - (C) Resistance after recovery: This indicates active immunity, as the body's immune system has responded to and learned from an infection. - (D) Resistance after vaccination: This is active immunity, as the immune system is stimulated to develop a response. - (E) Having antibodies but being ill: This is not a clear example of immunity as it indicates immune system failure.

Step 3: Select the Correct Answer

Based on the understandings from Step 1 and Step 2, option (B) is the correct example of passive immunity, where antibodies are passively transferred from a mother to her baby.

Key Concepts

Antibodies Transfer

The process of antibody transfer is a key component of passive immunity. Unlike active immunity, where the body's immune system produces antibodies in response to an antigen, passive immunity involves direct transfer of antibodies from one individual to another.
In the context of the exercise, option (B) "Babies who are nursing receive antibodies from their mothers" is a classic example. Through breast milk, especially colostrum, mothers pass on antibodies like IgA to their infants, giving them temporary protection against certain infections.
These antibodies provide immediate but short-lasting protection, as they do not involve any immune system memory formation. Here are some key points about antibody transfer:

• Fast-acting: Offers immediate protection.
• Temporary: Lasts only for a few weeks to months.
• No memory: The body does not "learn" from the antibodies.

This type of immunity is particularly crucial in the early months of life when the infant's immune system is still maturing.

Nursing and Immunity

Nursing plays a critical role in transferring immunity from mother to child. Breast milk is a rich source of antibodies, particularly during the initial days after birth. The first milk, colostrum, is packed with protective antibodies that help safeguard the newborn.
By breastfeeding, mothers provide vital immunological benefits:

• Protection against gastrointestinal infections.
• Reduced risk of respiratory infections.
• Fortification of the infant’s underdeveloped immune system.

Though the immunity conferred by nursing is passive and temporary, it supports the child until their own immune system becomes fully functional. It also primes the infant's immune system to respond more efficiently to future challenges.

Active vs Passive Immunity

To understand the distinction between active and passive immunity, it's crucial to grasp how immunity is acquired. Active immunity involves the body’s own production of antibodies in response to an infection or vaccination. This process takes time, as the immune system needs to identify the antigen and mount a response. Once developed, active immunity tends to last long, sometimes for life, by creating memory cells.
Passive immunity, on the other hand, involves the direct transfer of antibodies, as seen in instances like receiving antivenom for a snake bite or from maternal antibodies via nursing. It's an immediate form of protection but does not result in the creation of memory cells.
Here's how they differ:

• Active Immunity: Long-lasting, memory-forming, self-produced antibodies. Examples include recovery from infections and vaccinations.
• Passive Immunity: Immediate, short-term, borrowed antibodies. Examples include maternal antibody transfer, immunoglobulin treatments.

Both forms of immunity play important roles at different life stages and situations.

Immune System Function

The immune system is a complex network designed to fend off pathogens such as bacteria, viruses, and parasites. It consists of various cells, tissues, and organs that work together to protect the body. The system functions in a coordinated manner, employing various strategies to keep the body healthy.
One of its primary functions is to recognize and eliminate anything it perceives as foreign. This includes pathogens and potentially harmful substances.
Key components of the immune system include:

• White blood cells: Such as lymphocytes, which include B-cells (producing antibodies) and T-cells (directly attacking infected cells).
• Antibodies: Proteins that specifically recognize and bind to antigens, marking them for destruction.
• Organs and tissues: Such as lymph nodes and the spleen, which filter pathogens from the blood and tissue fluids.

The immune system's ability to distinguish between "self" and "non-self" items makes it effective yet complex, necessitating both active and passive defense mechanisms for optimal protection.