Cell-mediated immunity

Definition

Cell-mediated immunity is a type of adaptive immune response primarily involving T cells that target and eliminate infected or abnormal cells, playing a crucial role in defending against viral infections. This immunity operates without antibodies, relying instead on direct cell-to-cell interactions to destroy pathogens or infected host cells. It is especially important in controlling intracellular pathogens like viruses and is vital for the body’s defense mechanisms during both acute and chronic infections.

5 Must Know Facts For Your Next Test

1. Cell-mediated immunity is essential for clearing viral infections, especially those caused by intracellular pathogens that replicate within host cells.
2. Cytotoxic T lymphocytes (CTLs) are a key component of cell-mediated immunity, directly killing virus-infected cells by recognizing specific antigens presented on their surface.
3. Helper T cells enhance the immune response by releasing cytokines that activate other immune cells, including B cells and macrophages.
4. The development of memory T cells after an infection allows for a faster and stronger response upon re-exposure to the same pathogen.
5. In chronic viral infections, such as HIV, the effectiveness of cell-mediated immunity can be compromised, leading to persistent viral replication and ongoing disease progression.

Review Questions

• How do T cells contribute to the elimination of viruses during cell-mediated immunity?
  • T cells contribute to eliminating viruses by recognizing and binding to specific viral antigens presented on infected cells. Cytotoxic T lymphocytes (CTLs) are particularly important, as they directly kill these infected cells through mechanisms like apoptosis. Additionally, helper T cells support this process by releasing cytokines that enhance the overall immune response, ensuring a coordinated attack against the virus.
• Discuss the role of cytokines in enhancing cell-mediated immunity during viral infections.
  • Cytokines play a crucial role in cell-mediated immunity by acting as signaling molecules that facilitate communication between immune cells. During viral infections, cytokines released by helper T cells can stimulate the activation and proliferation of cytotoxic T lymphocytes, enhancing their ability to target infected cells. They also help recruit other immune components such as macrophages, further amplifying the immune response against the virus.
• Evaluate how chronic viral infections impact the effectiveness of cell-mediated immunity and potential therapeutic approaches.
  • Chronic viral infections can lead to functional exhaustion of T cells, diminishing their ability to respond effectively over time. This exhaustion is often characterized by reduced cytokine production and impaired cytotoxic activity. To address this challenge, therapeutic approaches such as immune checkpoint inhibitors aim to rejuvenate exhausted T cells and restore their functionality. Understanding these dynamics is crucial for developing effective treatments for persistent viral infections.

Related terms

T cells:

A type of white blood cell that plays a central role in cell-mediated immunity by recognizing and destroying infected cells.

Cytokines: Signaling proteins released by immune cells that facilitate communication between cells during immune responses, influencing the activation and differentiation of T cells.

Antigen-presenting cells (APCs): Cells that process and present antigens to T cells, initiating and regulating the cell-mediated immune response.