An Overview of T Cell Development
T Cells Role in the Immune System
T cells are critical to the human immune system, defending the body against infection from bacteria or viruses and from the development of cancers. T cells are white blood cells that play a significant role in human adaptive immunity, the specified and targeted immunity humans build throughout their lives.
T cells recognize potentially harmful molecules in the form of antigens, small proteins from foreign sources that trigger an immune response. Once a threat is identified, T cells work together with other immune cells to destroy the invading pathogen via an inflammatory response.
After the foreign particles are eliminated and the risk of infection decreases, T cells regulate the immune response, bringing it to a halt. A small population of T cells will continue to survey the bloodstream as memory T cells in the case of re-exposure.
There are many types of T cells found in the body, each with unique effector or regulatory functions. CD8+ T cells, or cytotoxic T cells, facilitate cell-mediated immunity by directly destroying infected or cancerous cells by releasing cytotoxins that trigger apoptosis.
Helper T cells exhibit surface protein CD4 and are responsible for recognizing and initiating an immune response. They communicate with other immune cells to alert them of the risk of infection by releasing signaling chemical messengers, such as cytokines. Once the inflammation caused by the immune response is no longer needed to eliminate a threat the formation of memory T cells occurs, and e apoptosis of most of the remaining effector T cells takes place.
T Cell Development: Origins and Locations
T cells develop from hematopoietic stem cells originating in the bone marrow. Early precursor cells will travel to the thymus, where they will differentiate into precursor T cells. These precursor cells are also called thymocytes and can be important in studies of early immune cells and T cell development.
T cells get their name from the development period that takes place in the thymus, thymus (T) cells. The many steps of T cell development ensure that only fully functional T cells exit the thymus.
Double-Negative Stage: T Cell Progenitors
Once the thymocytes enter the thymus, they undergo gene rearrangement to form their unique T cell receptor (TCR), which allows them to interact with and recognize antigens. Before this step, the thymocytes are considered immature and do not exhibit TCR, CD4, or CD8 receptors. Equipped with TCR, the now double-negative thymocytes undergo beta selection.
During beta selection, the gene rearrangement is tested and only the T cell that can successfully transcribe TCR moves forward in development. TCR is essential to the function of T cells and all T cells must exhibit a properly assembled TCR to move into the double positive stage. The beta-selection checkpoint is an important marker in T cell development, determining which thymocytes will undergo apoptosis in the thymus.
Double-Positive Stage and Positive Selection
During this development portion, thymocytes have CD4 and CD8 co-receptors on their cell surface. Double-positive thymocytes undergo positive selection, a test of the ability of their TCR to signal properly.
During positive selection, double-positive cells interact with a type of antigen-presenting complex (APC) made up of thymic epithelial cells (TECs) and major histocompatibility molecules (MHCs). Double-positive cells that do not accurately recognize self-antigens receive an apoptosis signal and do not move on in the development process.
Single-Positive Stage and Negative Selection
The thymocytes are now fully equipped with their unique surface receptors and co-receptors and can accurately differentiate between self and non-self antigens. Next, the precursor T cells will undergo a lineage commitment where they become either CD4+ or CD8+ T cells and lose one of their co-receptors. This is determined by their innate interactions with the MHC classes. Interacting with MHC class II leads to helper T cells, while MHC class I leads to cytotoxic T cells.
This stage is called single-positive because only one co-receptor is activated and retained.
Negative selection is a crucial step in T cell development, pinpointing autoreactive thymocytes. T cell progenitors that are strongly reactive against self-antigens are eliminated to promote self-tolerance. If these cells were circulating the bloodstream, they could launch an immune response against the body’s own tissues.
Maturation, Egress, and T Cell Function
The now fully mature T cells migrate to the periphery and begin circulating the bloodstream and lymphatic system, ready to respond to their specific antigen. They continue to actively contribute to the immune response, primarily detecting and responding to foreign antigens. Mature T cells demonstrate well-developed self-tolerance and properly functioning TCRs, and maintaining the T cell population is integral to maintaining a balanced immune system.
Significance of T Cell Development
Understanding the complexities of T cell development is an essential tool in the study of immune function and disease prevention. Because T cells are so fundamental to the immune system and inflammatory response, studying T cell development provides insight into how T cells are generated, mature, and regulated, deepening our understanding of the immune response overall.
Dysfunction during T cell maturation can lead to numerous immune system disorders, including autoimmune disorders and immunodeficiency. Scientists look to T cell development studies to identify how these diseases form and how they can be treated and prevented.
T cells are commonly used in cutting-edge research developments in immunotherapy. Adoptive T cell therapy and chimeric antigen receptor (CAR) T cell therapy rely on a clear understanding of T cell development to accurately extract, expand, and activate T cells in the laboratory for clinical use. Vaccine development also utilizes knowledge of T cell development to gauge the immunogenicity of vaccines and provide more long-lasting protection against infections.
T Cell Development Studies Using Microbubble Technology
Accessing T cell populations for research and therapeutic purposes can present many challenges in supply, storage, and safe processing. At Akadeum, we understand the importance of a simple and easy-to-use cell separation method and provide precisely that with our innovative microbubble technology.
Isolate T cells using our broad range of T cell kits that leave T cells of interest untouched by gently floating away unwanted cells. We offer kits targeted to separate a variety of T cells from both mouse and human samples. We also offer specialized kits for isolating pure T cell populations directly from leukopaks.
Explore all of Akadeum’s T cell isolation products or contact our team with your project goals to find the best cell separation solution for your sample types.