Question

Which of the following do not participate in adaptive immunity? a. B cells c. macrophages b. mast cells d. all of the above

Short answer

b. mast cells

Step-by-step solution

Define Adaptive Immunity

Adaptive immunity, also known as acquired immunity, is the body's ability to recognize and defend itself against distinct invaders and their products. Key components of adaptive immunity include B cells, T cells, and antibodies.

Identify Cells Involved in Adaptive Immunity

B cells are a type of white blood cell that plays a significant role in adaptive immunity by producing antibodies. T cells, another category of white blood cells, assist in recognizing and attacking pathogens.

Analyze Each Option

a. B cells: These are directly involved in adaptive immunity. c. Macrophages: These cells are part of innate immunity but can play a role in presenting antigens to T cells, thus indirectly supporting adaptive immunity. b. Mast cells: These cells are a part of the innate immune system and are primarily involved in allergic reactions.

Determine Correct Answer

Considering the roles of B cells (direct involvement in adaptive immunity), macrophages (indirect support through antigen presentation), and mast cells (no direct role in adaptive immunity), mast cells do not participate in adaptive immunity.

Key concepts

B cells

B cells are a critical component of the adaptive immune system. They originate from bone marrow and mature there as well. Once activated by the presence of a pathogen, B cells divide into plasma cells and memory B cells.

Plasma cells are responsible for producing antibodies, which are specialized proteins that can neutralize or mark pathogens for destruction.

• Antibodies bind to specific antigens on pathogens.
• They neutralize the pathogen or mark it for destruction by other immune cells.

Memory B cells play a crucial role in providing long-lasting immunity. They 'remember' the specific antigens of pathogens encountered previously, allowing for a faster and more effective response upon future exposures to the same pathogen.

Thus, by producing antibodies and maintaining immunological memory, B cells are essential for the body’s ability to fight off infections.

T cells

T cells are another vital component of the adaptive immune system. These cells originate from the bone marrow but mature in the thymus, which is why they are called 'T' cells. T cells are divided into two main types: Helper T cells (Th cells) and Cytotoxic T cells (Tc cells).

Helper T cells are like the managers of the immune response

• They coordinate the activity of other immune cells by releasing signaling molecules called cytokines.
• They help activate B cells and Cytotoxic T cells.

Cytotoxic T cells have a more direct role in combating infections

• They identify and destroy infected cells.
• They bind to antigens presented on the surface of infected cells and induce cell death.

T cells are crucial for identifying and eliminating pathogens that have invaded cells, thus playing a significant role in adaptive immunity. Their ability to recognize and respond to highly specific antigens makes them indispensable for immune defense.

Macrophages

Macrophages are primarily associated with innate immunity but also play a supporting role in adaptive immunity. These cells are derived from monocytes, a type of white blood cell, and are present in almost all tissues of the body.

In their role in innate immunity

• Macrophages engulf and digest pathogens through a process called phagocytosis.
• They release cytokines to recruit other immune cells to the site of infection.

In adaptive immunity, macrophages act as antigen-presenting cells (APCs)

• They digest pathogens and present fragments called antigens on their surface.
• This presentation helps activate T cells which then further initiate adaptive immune responses.

Even though macrophages are primarily part of the innate immune system, their role in antigen presentation is crucial for the activation and function of the adaptive immune system. This interaction ensures a more powerful and targeted response against pathogens.