Cell-mediated immunity

Definition

Cell-mediated immunity is a crucial aspect of the adaptive immune response that involves the activation of T lymphocytes, which play a key role in defending the body against intracellular pathogens, such as viruses and some bacteria. This type of immunity does not rely on antibodies but instead involves direct cell-to-cell interactions and the release of cytokines to eliminate infected cells and coordinate the immune response. It is essential for recognizing and responding to cells that have been altered by infection or cancer.

5 Must Know Facts For Your Next Test

1. Cell-mediated immunity is primarily mediated by cytotoxic T cells, which directly kill infected or cancerous cells.
2. Helper T cells are essential for orchestrating the immune response, as they stimulate B cells to produce antibodies and activate other immune cells.
3. The recognition of infected cells by T cells requires antigen presentation, where pieces of the pathogen (antigens) are displayed on major histocompatibility complex (MHC) molecules on the surface of infected cells.
4. In addition to eliminating infected cells, cell-mediated immunity also plays a role in tissue repair and regulation of the immune response through cytokine signaling.
5. Cell-mediated immunity is particularly important in combating viral infections and some forms of cancer, making it a critical component of overall immune function.

Review Questions

• How do T lymphocytes contribute to cell-mediated immunity and what roles do different types of T cells play?
  • T lymphocytes are pivotal in cell-mediated immunity. Cytotoxic T cells directly attack and destroy infected or cancerous cells by recognizing specific antigens presented on these cells. Helper T cells enhance the immune response by releasing cytokines that activate B cells and stimulate other immune cells, ensuring a robust defense against pathogens. Together, they work in tandem to ensure effective cellular responses to infections.
• Discuss the importance of antigen presentation in initiating a cell-mediated immune response.
  • Antigen presentation is vital for initiating a cell-mediated immune response because it allows T lymphocytes to recognize specific antigens associated with pathogens. Antigen-presenting cells (APCs) display these antigens on major histocompatibility complex (MHC) molecules, which are recognized by T cell receptors. This interaction activates T cells, enabling them to proliferate and differentiate into effector cells that can combat infections effectively.
• Evaluate the role of cytokines in coordinating the activities of various immune cells during cell-mediated immunity.
  • Cytokines play a critical role in coordinating the activities of various immune cells during cell-mediated immunity by acting as signaling molecules that facilitate communication between them. They are produced by activated T cells and other immune cells and influence processes such as inflammation, differentiation of T cells, and activation of B cells. This regulatory network ensures that the immune response is efficient and appropriately targeted, preventing overreaction or failure to respond to pathogens.

Related terms

T lymphocytes:

A type of white blood cell that plays a central role in cell-mediated immunity, including helper T cells and cytotoxic T cells.

Cytokines:

Signaling proteins released by immune cells that help to regulate the immune response, including inflammation and the activation of other immune cells.

Antigen presentation: The process by which antigen-presenting cells display antigens on their surface to activate T lymphocytes, leading to a specific immune response.