Cellular immunity

Definition

Cellular immunity is a type of immune response that relies on the activation of immune cells, particularly T cells, to fight off pathogens and infected cells. This process involves the recognition of specific antigens presented by infected or abnormal cells, leading to the activation and proliferation of T cells, which then carry out targeted attacks on these cells. It plays a critical role in protecting the body against viral infections and cancer by directly eliminating compromised cells and coordinating the immune response.

5 Must Know Facts For Your Next Test

1. Cellular immunity primarily involves T cells, which can be further divided into helper T cells (CD4+) and cytotoxic T cells (CD8+), each with distinct functions in combating infections.
2. The process begins when antigen-presenting cells display foreign antigens on their surface using major histocompatibility complex (MHC) molecules, which are recognized by T cell receptors.
3. Helper T cells release cytokines that stimulate the activation of other immune cells, while cytotoxic T cells directly kill infected or malignant cells through mechanisms such as inducing apoptosis.
4. Vaccines that elicit a strong cellular immune response often include live attenuated pathogens or subunit vaccines that contain specific antigens to effectively prime T cell activity.
5. Memory T cells are generated after an initial infection or vaccination, allowing for a faster and more robust response upon re-exposure to the same pathogen.

Review Questions

• How do T cells contribute to cellular immunity and what are the different types involved?
  • T cells are essential for cellular immunity as they specifically recognize and respond to antigens presented by infected or abnormal cells. There are two main types of T cells: helper T cells (CD4+) that activate other immune responses by releasing cytokines, and cytotoxic T cells (CD8+) that directly destroy infected or cancerous cells. This differentiation allows for a coordinated attack against pathogens while also ensuring the immune system is properly regulated.
• Discuss the role of antigen-presenting cells in initiating the cellular immune response.
  • Antigen-presenting cells (APCs) play a vital role in activating T cells by processing and displaying foreign antigens on their surface through major histocompatibility complex (MHC) molecules. This presentation is crucial because it allows T cell receptors to recognize specific antigens, leading to T cell activation and proliferation. Without APCs, the initiation of a robust cellular immune response would be severely impaired, highlighting their importance in immunology.
• Evaluate how vaccines designed to enhance cellular immunity can impact long-term protection against diseases.
  • Vaccines that focus on enhancing cellular immunity aim to generate strong memory T cell responses against specific pathogens. By using live attenuated viruses or subunit proteins that mimic infections, these vaccines effectively prime the immune system for future encounters with real pathogens. This preparation leads to a quicker and more effective immune response upon re-exposure, resulting in long-term protection against diseases such as viral infections and certain cancers. The strategic design of these vaccines emphasizes the importance of cellular immunity in achieving lasting immunity.

Related terms

T cells:

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

Antigen-presenting cells (APCs): Cells that capture, process, and present antigens to T cells, crucial for the initiation of the cellular immune response.

Cytokines:

Signaling molecules produced by immune cells that mediate and regulate immunity, inflammation, and hematopoiesis, playing an essential role in the communication between T cells and other immune components.