Cell-mediated immunity

Definition

Cell-mediated immunity is a type of adaptive immune response that involves the activation of T cells to directly combat infected or abnormal cells. This form of immunity plays a crucial role in defending against intracellular pathogens, such as viruses and some bacteria, as well as tumor cells. Unlike humoral immunity, which relies on antibodies produced by B cells, cell-mediated immunity is characterized by the direct involvement of immune cells that identify and destroy compromised cells in the body.

5 Must Know Facts For Your Next Test

1. Cell-mediated immunity primarily involves T cells, which are differentiated into various subtypes, including helper T cells and cytotoxic T cells, each with unique functions.
2. This type of immunity is essential for controlling infections caused by intracellular pathogens like viruses, as these pathogens replicate within host cells where antibodies cannot reach them.
3. Cytotoxic T cells recognize and bind to infected or abnormal cells through specific receptors, leading to the destruction of those cells via mechanisms such as apoptosis.
4. Helper T cells enhance the immune response by releasing cytokines that activate other immune cells, including B cells and macrophages, creating a coordinated attack against pathogens.
5. Memory T cells are generated after an initial infection, allowing for a faster and more effective response upon re-exposure to the same pathogen.

Review Questions

• How do T cells contribute to the overall effectiveness of cell-mediated immunity?
  • T cells play a pivotal role in cell-mediated immunity by directly identifying and eliminating infected or abnormal cells. Cytotoxic T cells are specialized for this task, recognizing specific antigens presented on the surface of compromised cells and inducing their death through various mechanisms. Helper T cells support this process by releasing cytokines that enhance the activation and function of other immune components, ensuring a robust and coordinated immune response.
• What role do antigen presenting cells (APCs) play in initiating cell-mediated immunity?
  • Antigen presenting cells (APCs) are crucial for kickstarting cell-mediated immunity because they process foreign antigens and present them on their surface for recognition by T cells. When an APC encounters a pathogen, it engulfs it and displays its antigens using major histocompatibility complex (MHC) molecules. This interaction is essential for activating naïve T cells, allowing them to differentiate into effector T cells that can respond effectively to the pathogen.
• Evaluate the importance of memory T cells in the context of infectious diseases and vaccination strategies.
  • Memory T cells are vital for long-term protection against infectious diseases, as they provide a faster and stronger immune response upon re-exposure to previously encountered pathogens. This characteristic is particularly important for vaccination strategies that aim to prime the immune system without causing disease. By generating memory T cells after vaccination, individuals can achieve quick and effective responses to actual infections, significantly reducing morbidity and mortality associated with infectious diseases.

Related terms

T cells: A type of white blood cell that plays a central role in cell-mediated immunity, including helper T cells that assist other immune cells and cytotoxic T cells that kill infected or cancerous cells.

Antigen presenting cells (APCs): Cells that process and present antigens on their surface to T cells, thereby initiating a specific immune response; examples include dendritic cells and macrophages.

Cytokines: Signaling proteins released by immune cells that modulate the immune response, including the activation and proliferation of T cells during cell-mediated immunity.