Types of T Cells to Know for Immunobiology

T cells are vital players in our immune system, each with unique roles. From activating other immune cells to directly killing infected cells, they help tailor responses to various threats, ensuring effective protection and long-lasting immunity against diseases.

1. CD4+ T helper cells (Th cells)

   • Play a crucial role in orchestrating the immune response by activating other immune cells, including B cells and CD8+ T cells.
   • Differentiate into various subsets (e.g., Th1, Th2, Th17) that produce specific cytokines to tailor the immune response to different pathogens.
   • Essential for the development of long-term immunity and the formation of memory cells.

2. CD8+ Cytotoxic T cells (CTLs)

   • Responsible for directly killing infected or cancerous cells by recognizing specific antigens presented by MHC class I molecules.
   • Release cytotoxic granules containing perforin and granzymes to induce apoptosis in target cells.
   • Play a key role in controlling viral infections and tumor surveillance.

3. Regulatory T cells (Tregs)

   • Maintain immune tolerance by suppressing excessive immune responses and preventing autoimmunity.
   • Express the transcription factor FoxP3, which is critical for their development and function.
   • Help regulate the activity of other T cells and maintain homeostasis within the immune system.

4. Memory T cells

   • Formed after an initial immune response, these cells provide rapid and robust protection upon re-exposure to the same antigen.
   • Can be classified into central memory T cells (Tcm) and effector memory T cells (Tem), each with distinct roles in immune surveillance.
   • Essential for long-lasting immunity and the effectiveness of vaccines.

5. Natural killer T cells (NKT cells)

   • Bridge the innate and adaptive immune systems by recognizing lipid antigens presented by CD1d molecules.
   • Can rapidly produce cytokines and exert cytotoxic effects, contributing to the early immune response.
   • Play a role in tumor immunity and the regulation of autoimmune diseases.

6. Gamma delta T cells (γδ T cells)

   • Possess a unique T cell receptor (TCR) that allows them to recognize a wide range of antigens, including non-peptide antigens.
   • Found in various tissues, particularly at mucosal surfaces, and play a role in the first line of defense against infections.
   • Involved in tissue repair and the regulation of immune responses.

7. T follicular helper cells (Tfh cells)

   • Specialized CD4+ T cells that provide help to B cells in germinal centers, promoting antibody production and affinity maturation.
   • Produce cytokines such as IL-21, which are critical for B cell differentiation and class switching.
   • Essential for the development of long-lived plasma cells and memory B cells, contributing to humoral immunity.