Cell-Mediated Immunity

Definition

Cell-mediated immunity is a crucial part of the immune response that involves T cells (a type of white blood cell) and is essential for defending against intracellular pathogens such as viruses and certain parasites. This type of immunity is particularly important for recognizing and eliminating infected cells and coordinating the immune response, thus playing a key role in combating infections caused by various parasites, including protozoa and helminths.

5 Must Know Facts For Your Next Test

1. Cell-mediated immunity is primarily facilitated by CD4+ helper T cells and CD8+ cytotoxic T cells, which are crucial for fighting infections caused by intracellular pathogens.
2. In parasitic infections, cell-mediated immunity helps to eliminate parasites that reside within host cells, enhancing the body's ability to fight off diseases like malaria and leishmaniasis.
3. The activation of T cells requires antigen recognition presented by major histocompatibility complex (MHC) molecules on antigen-presenting cells.
4. Cytokines produced by T cells enhance the immune response by recruiting other immune cells to sites of infection, leading to a more effective elimination of pathogens.
5. Dysregulation of cell-mediated immunity can lead to immunopathology, where an excessive or inadequate immune response causes tissue damage or ineffective clearance of parasites.

Review Questions

• How do T cells contribute to the elimination of intracellular parasites through cell-mediated immunity?
  • T cells play a vital role in eliminating intracellular parasites by recognizing infected host cells through specific receptors. CD8+ cytotoxic T cells directly kill these infected cells, while CD4+ helper T cells release cytokines that stimulate other immune responses. This coordinated action enhances the body's ability to control and eradicate infections caused by protozoa and other intracellular pathogens.
• Discuss the mechanisms used by parasites to evade cell-mediated immunity and how this affects the overall immune response.
  • Parasites employ various strategies to evade cell-mediated immunity, such as altering their surface antigens to avoid detection by T cells or inhibiting antigen presentation on MHC molecules. These evasion tactics can significantly impair the immune system's ability to mount an effective response, leading to chronic infections. This ongoing battle between parasites and the immune system highlights the complexity of host-pathogen interactions.
• Evaluate the impact of cell-mediated immunity on immunopathology during parasitic infections, including how this can lead to disease manifestations.
  • Cell-mediated immunity can contribute to immunopathology in parasitic infections when the immune response is overly aggressive or misdirected. For instance, excessive activation of T cells can cause tissue damage and inflammation, leading to symptoms such as fever and pain. Additionally, in certain cases like schistosomiasis, the immune response can result in fibrosis and organ dysfunction due to chronic inflammation, demonstrating how an essential protective mechanism can also lead to adverse outcomes in parasitic diseases.

Related terms

T Cells: A subtype of lymphocytes that play a central role in cell-mediated immunity by recognizing infected or abnormal cells and orchestrating immune responses.

Cytokines: Small proteins released by cells that have a specific effect on the interactions and communications between immune system cells, influencing the immune response.

Antigen Presentation: The process by which antigen-presenting cells display antigens on their surface to T cells, initiating the adaptive immune response.