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Chapter 33: Problem 8

What is the function of major histocompatibility class (MHC) I molecules? a. MHC I molecules assist with strengthening the cell membrane. b. MHC I molecules present antigens on the surface of a cell. c. MHC I molecules allow movement of materials across the cell membrane. d. MHC I molecules provide signals for processes involved in cell division

Short Answer

Expert verified
b. MHC I molecules present antigens on the surface of a cell.

Step by step solution

01

Understand the Function of MHC I Molecules

Major Histocompatibility Complex (MHC) class I molecules are proteins found on the surface of all nucleated cells. Their primary role is to present peptide antigens to the immune cells, particularly cytotoxic T cells.
02

Eliminate Incorrect Options

Analyze each option based on the primary role of MHC I molecules. Option a mentions strengthening the cell membrane, which is not the role of MHC I. Option c discusses moving materials across the cell membrane, again unrelated to MHC I. Option d involves signals for cell division, which is also not pertinent to MHC I.
03

Identify the Correct Option

Recall that MHC I molecules present peptide fragments from inside a cell to the immune system. This function fits perfectly with option b.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

antigen presentation
Antigen presentation is a key process in the immune system. It involves the display of protein fragments, called antigens, on the surface of cells. This helps the immune system recognize and respond to threats.

MHC I molecules play an essential role in this process. They bind to peptide fragments generated from proteins within the cell. Then, they move these fragments to the cell surface. Here, they present the antigens to cytotoxic T cells.

This presentation is crucial because it allows cytotoxic T cells to identify infected or abnormal cells. Without antigen presentation, the immune system would struggle to detect internal cell threats, such as viruses, some bacteria, and cancerous changes.

immune system
The immune system is our body's defense mechanism against infections and diseases. It consists of various components that work together to protect us.

The primary cells of the immune system include:
  • B cells and T cells, which are types of lymphocytes
  • Phagocytes like macrophages
  • Natural killer cells

The immune system has two main types of responses: innate and adaptive. The innate immune response is the body's first line of defense, providing immediate but non-specific protection. The adaptive immune response is slower but more specific. It involves the creation of memory cells to recognize and respond more effectively to previous threats.

MHC I molecules are integral to the adaptive immune response. They help cytotoxic T cells recognize and destroy infected or abnormal cells.

cytotoxic T cells
Cytotoxic T cells, also known as CD8+ T cells, are crucial players in the immune system. Their main job is to kill infected or cancerous cells.

These T cells have receptors on their surface that can recognize antigens presented by MHC I molecules. When a cytotoxic T cell encounters a cell displaying a foreign or abnormal antigen, it binds to the antigen-MHC I complex.

Once bound, the cytotoxic T cell releases enzymes that create pores in the target cell's membrane. It then injects toxic substances into the cell, leading to its destruction.

This process ensures that infected cells are quickly eliminated, preventing the spread of infections or uncontrolled cell growth, like in cancer.

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Most popular questions from this chapter

How do natural killer cells react to healthy cells compared to cells infected with a pathogen? a. Natural killer cells recognize MHC I on a healthy cell and do not kill it, while the infected cells that do not present MHC I are killed. b. Natural killer cells recognize MHC I on an infected cell and kill it, while the healthy cells that do not present MHC I are not killed. c. Natural killer cells recognize MHC II on a healthy cell and do not kill it, while the infected cells that do not present MHC II are killed. d. Natural killer cells recognize MHC II on an infected cell and kill it, while the healthy cells that do not present MHC II are not killed.

What function does the diversity of the variable region of an antibody help it perform? a. It helps in communication of antibodies with other components of immune system. b. It helps the antibodies to function with very low affinity and specificity. c. It enables many different antibodies to be made that all have different specificities of binding. d. It enables many different antibodies to be made that all have same specificities of binding.

Why does the human body need more than its skin to function as a barrier to infecting pathogens? a. Skin works only against some types of bacteria. To prevent the entry of other pathogens, other physical or chemical barriers are needed. b. Skin does not provide a broad coverage against invasion of the body by any foreign particle, so it is not a very effective barrier. c. Pathogens could enter the body through several places that are not covered by skin that need to have a barrier to prevent infection. d. Skin acts only as a chemical barrier against pathogens. The body also needs physical barriers to prevent various types of infection.

Why do antibodies isolated from the same individual show a variety of constant domains? a. The antibodies were synthesized in response to infections by different pathogens. b. The antibodies were transmitted as the result of passive immunity. c. The antibodies have different specificities of antigen binding. d. The antibodies belong to different classes of immunoglobulin molecules.

What is the difference between natural killer cells and macrophages? a. Natural killer cells are not always present in the body and must be induced, whereas macrophages are constantly present. b. Natural killer cells actually kill foreign cells, whereas macrophages serve only a signaling function. c. Only macrophages can invade host tissues to fight foreign cells that make their way into those tissues. d. Natural killer cells kill foreign cells through the processes of lysis and proteolysis, whereas macrophages kill foreign cells by phagocytosis.
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