Cell-mediated immunity

Definition

Cell-mediated immunity is a type of adaptive immune response that primarily involves T cells in recognizing and responding to infected or abnormal cells. This immune mechanism is crucial for defending against intracellular pathogens like viruses and certain bacteria, as well as for the elimination of cancerous cells. The activation and differentiation of T cells, the various subsets they form, and their roles in vaccination, histocompatibility, and transplant rejection are all important aspects of understanding how cell-mediated immunity operates.

5 Must Know Facts For Your Next Test

1. T cell activation occurs when naive T cells recognize specific antigens presented on major histocompatibility complex (MHC) molecules by antigen presenting cells.
2. There are two main types of T cells involved in cell-mediated immunity: cytotoxic T cells that kill infected cells and helper T cells that assist other immune cells.
3. Vaccination strategies often aim to elicit a strong cell-mediated immune response by ensuring effective T cell activation and memory formation.
4. Histocompatibility is essential for successful organ transplantation; the immune system's recognition of foreign antigens can lead to graft rejection if cell-mediated responses are triggered.
5. Transplant rejection can be classified into hyperacute, acute, and chronic types, all of which involve different mechanisms of cell-mediated immunity.

Review Questions

• How does the activation of T cells contribute to the effectiveness of cell-mediated immunity?
  • T cell activation is fundamental to the effectiveness of cell-mediated immunity. When naive T cells encounter their specific antigen presented on MHC molecules by antigen presenting cells, they undergo activation and differentiation. This leads to the proliferation of effector T cells that can either directly kill infected or cancerous cells or help orchestrate other components of the immune response. Understanding this process highlights how vital T cell interactions are in controlling infections and maintaining cellular integrity.
• Discuss the different roles of cytotoxic T cells and helper T cells in the context of cell-mediated immunity.
  • Cytotoxic T cells play a critical role in directly targeting and eliminating infected or cancerous cells through recognition of specific antigens presented on MHC class I molecules. In contrast, helper T cells assist in amplifying the immune response by secreting cytokines that activate B cells and enhance the activity of cytotoxic T cells and macrophages. Together, these subsets work synergistically to provide a robust defense against pathogens and abnormal cell growth.
• Evaluate the impact of histocompatibility on transplant success and how it relates to cell-mediated immunity.
  • Histocompatibility is crucial for transplant success because it determines how the recipient's immune system will react to the donor tissue. If there are significant differences in MHC molecules between donor and recipient, the recipient's cytotoxic T cells may recognize the transplanted tissue as foreign and initiate a strong cell-mediated immune response, leading to graft rejection. This evaluation highlights the importance of matching donor-recipient pairs to minimize immune reactions and improve transplant outcomes.

Related terms

Cytotoxic T cells:

A subset of T cells that directly kill infected or cancerous cells by recognizing specific antigens presented by these cells.

Helper T cells: A subset of T cells that support other immune cells by secreting cytokines, enhancing the immune response against pathogens.

Antigen presenting cells (APCs): Cells that capture, process, and present antigens to T cells, playing a crucial role in initiating cell-mediated immunity.