Question

Certain diseases affecting tissue perfusion can have a profound effect on the efficiency of the immune system. Poor oxygen delivery would hamper which of the following immunoprotective events? A. Antigen presentation by natural killer cells B. Respiratory burst by macrophages C. Antibody production by B cells D. T cell maturation in the thymus

Short answer

B. Respiratory burst by macrophages

Step-by-step solution

Understand Tissue Perfusion and Immune Function

Tissue perfusion refers to the flow of blood through the tissues, supplying them with oxygen and nutrients. Efficient immune response requires adequate oxygen supply, as several immune functions are highly dependent on oxygen availability.

Identify Immune Functions Listed

Look at the given options and identify the immune functions mentioned: antigen presentation by natural killer cells, respiratory burst by macrophages, antibody production by B cells, and T cell maturation in the thymus.

Determine Oxygen Dependency

Consider which of these immune events specifically require a high amount of oxygen. For example, respiratory burst is an immune defense mechanism used by macrophages that produces reactive oxygen species to kill pathogens.

Select the Correct Answer

Given that respiratory burst by macrophages requires a high amount of oxygen to generate reactive oxygen species, poor oxygen delivery would most significantly affect this process. Therefore, the correct answer is B. Respiratory burst by macrophages.

Key concepts

Oxygen Dependency of Immune Functions

The human immune system relies heavily on oxygen to function optimally. Many critical immune responses need sufficient oxygen to proceed effectively. Oxygen helps in the production of energy, known as ATP (adenosine triphosphate), which powers various cellular activities. Without adequate oxygen, cells, including immune cells, can't generate the energy needed to perform their tasks.
For instance, several immune mechanisms such as the oxidative burst (also called respiratory burst), which helps destroy pathogens, are highly oxygen-dependent. When tissue perfusion is inadequate, these activities diminish, compromising the body’s ability to fight infections.

Respiratory Burst by Macrophages

Macrophages play a crucial role in the immune system by engulfing and destroying pathogens. One of the ways they do this is through a process called the respiratory burst. This is an immune defense mechanism where macrophages produce reactive oxygen species (ROS) to kill ingested pathogens.
During the respiratory burst, macrophages consume a lot of oxygen to generate ROS. These reactive molecules are highly effective at neutralizing bacteria and other microbes. Without a sufficient oxygen supply, macrophages can't produce enough ROS, thereby weakening the immune defense.
Therefore, diseases that impair tissue perfusion can significantly affect the respiratory burst, making it harder for the body to combat infections.

Immune System Oxygen Requirements

The immune system's need for oxygen extends beyond just macrophage function. Almost all immune cells, including T cells and B cells, require oxygen to perform their activities. Oxygen is also necessary for the glycolysis pathway, where glucose is converted into energy, and the subsequent oxidative phosphorylation in mitochondria.
This process is essential for the proliferation and activation of T cells when responding to infections.
When the oxygen supply is interrupted due to poor tissue perfusion, it affects multiple immune functions. This includes antigen presentation, cytokine production, and cell-mediated immunity, reducing the overall efficiency of the immune system.

Tissue Perfusion Role in Immunity

Tissue perfusion is the flow of blood through tissues, ensuring the delivery of oxygen and nutrients while removing waste products. Good tissue perfusion is vital for maintaining effective immune responses.
Blood carries oxygen from the lungs to tissues and immune cells. When tissue perfusion is compromised, the oxygen supply diminishes, affecting the energy production needed for immune functions.
This can lead to a reduced ability of immune cells to migrate to infection sites, produce antibodies, and execute other essential functions. Thus, maintaining adequate tissue perfusion is critical for a robust and efficient immune system.