Question

Memory B cells are a. cloned lymphocytes that are active in fighting subsequent infections. b. cloned lymphocytes that are active during a primary infection. c. NK cells that recognize cancer cells and destroy them. d. cells that produce antibodies. e. macrophages that have recognized self antigens.

Short answer

The correct answer is A. Memory B cells are cloned lymphocytes that are active in fighting subsequent infections.

Step-by-step solution

Understanding Cell Types

It's important to understand what each cell type does. NK cells usually function in defense against tumors and virally-infected cells. Macrophages, on the other hand, act as scavengers, engulfing old cells, bacteria, and foreign substances. Lastly, lymphocytes are white blood cells that play a central role in the body's immune response.

Analyzing each Option

Now let's look at each option. A. focuses on 'cloned lymphocytes that are active in fighting subsequent infections,' which corresponds to the functionality of memory B cells. Option B. is related to active lymphocytes during a primary infection, which characterizes how B cells initially respond, but Memory B cells are known specifically for their role in secondary responses. C. describes NK cells, not memory B cells. Option D. refers to the action of producing antibodies - this is performed by plasma cells, not memory B cells. Lastly, E. describes a function of macrophages, not memory B cells.

Picking the Correct Answer

Based on the provided info and our initial understanding of the cell types, the answer should be option A. 'Memory B cells' are indeed a type of lymphocyte that 'remembers' infections and is active in subsequent encounters with the same pathogen.

Key concepts

Lymphocytes

Lymphocytes are a type of white blood cell that play a vital role in the immune system. They are primarily responsible for the body's targeted immune response against pathogens. There are several types of lymphocytes, each with a unique function.

The two main classes are B cells and T cells. B cells are responsible for antibody production, which can specifically target viruses and bacteria. When B cells are exposed to a pathogen, they can differentiate into memory B cells or plasma cells. Memory B cells provide long-term immunity, as they retain a 'memory' of the pathogen and can respond quickly upon re-exposure. T cells, on the other hand, can directly kill infected cells or help coordinate the immune response. T cells are further categorized into helper T cells, cytotoxic T cells, and regulatory T cells, each with specific functions in the immune defense.

Immune Response

The immune response is the body's defense mechanism against harmful pathogens such as bacteria, viruses, and parasites. It consists of two main strategies: the innate immune response and the adaptive immune response.

The innate response occurs first, is non-specific, and does not provide long-lasting immunity. It includes barriers like the skin, and immune cells like macrophages and NK cells that attack invaders indiscriminately. The adaptive immune response is slower, but it's highly specific and leads to the development of long-term immunity. It involves the activation of lymphocytes, which recognize antigens presented on the surface of pathogens. This specific recognition allows the immune system to mount a strong and targeted response, including the production of antibodies by B cells, to clear the infection and protect the body from future encounters with the same pathogen.

Secondary Infections

Secondary infections refer to instances when an individual gets infected by the same pathogen after the primary infection has been cleared. Unlike primary infections, the immune system's response to secondary infections is generally more rapid and effective due to the presence of memory cells.

As a product of the adaptive immune response, memory B cells play a crucial role here. They remember the specific features of the invading pathogens. Upon re-exposure to the same pathogens, memory B cells quickly recognize them and initiate a faster and stronger immune response. This typically results in a less severe and shorter duration of the secondary infection, as the body can immediately call upon its tailored defenses without having to start from scratch.

Antibody Production

Antibody production is a critical aspect of the adaptive immunity that is primarily carried out by B cells. Antibodies, also known as immunoglobulins, are Y-shaped proteins that specifically bind to antigens—the unique molecules found on pathogens.

The binding of antibodies to antigens neutralizes the pathogens, making them easier targets for phagocytes, or signals other components of the immune system to attack. During an initial exposure to a pathogen, B cells differentiate into plasma cells that produce antibodies. Memory B cells, on the other hand, are generated during this primary response and persist in the body. Should the pathogen re-enter the body, these memory B cells can rapidly differentiate into plasma cells and produce a large number of the appropriate antibodies, contributing to a quicker resolution of the infection.