Pan T cell is the term for the most broad classification of T cells, which are identified by specific T cell markers found on the cell surface, T cells are the primary executors and controllers of immune response. Formed in the thymus, early T cells are called thymocytes, and will undergo many developmental stages before they are released into the bloodstream—or are active in an infection response.
Pan T cells are first differentiated by the expression of their TCR, or T cell receptor. They develop within the thymus through thymic selection—the process of generating T cells with unique surface receptors which have non-self antigen recognizing abilities—into helper CD4+, cytotoxic CD8+, and regulatory CD4+ T cells.
The abbreviation CD stands for cluster of differentiation, meaning a group of proteins or lipids that can be used to identify cells. Although there are many CD markers, CD4+ and CD8+ are the largest subgroups of pan T cells. Once differentiated into their roles, they navigate in their naive inactive state via the bloodstream through tissues and organs, ready to activate against a pathogen.
CD4+ T cells are commonly referred to as helper T cells and play a vital role in our adaptive immune response. Upon activation, caused by antigen recognition, naive T cells are activated to secrete cytokines that promote and steer the immune response. CD4+ T cells make up over 60% of the T cells found in our bodies and are ready to proliferate and combat infection at any moment. They are identified by the surface marker CD4 and can become more specific helper types, such as Th1, Th2, or Th17, which secrete different combinations of cytokines in order to more directly address the type of infection they are fighting. In addition, they can further differentiate into memory cells once the immune response has diminished.
These specialized memory cells continue to exist in small quantities in case of future infection or exposure to the same pathogen. As we age and expose our immune systems to more pathogens and antigens, our T cells learn and our adaptive immune response is strengthened.
Human cells also possess naturally occurring antigens called self-antigens, an antigen is a molecule that causes an immune response. Our immune cells are specially equipped to differentiate between self and non-self antigens. Some CD4+ cells will also develop into regulatory T cells, which inhibit the immune system’s inflammatory response. These regulatory T cells are essential because they moderate our immune response to protect our healthy cells and prevent damage from unregulated immune responses.
CD8+ T cells are also called cytotoxic T cells and function as our cell-to-cell combat against infections. These effector cells mediate our adaptive response and kill anomalous cells. Cytotoxic T cells can induce apoptosis—programmed cell death—in cancer cells, viral or bacterially infected cells, and damaged cells. They can bind to their antigens using their T cell receptor in combination with the glycoprotein CD8, a coreceptor that facilitates the cytotoxic T cells’ exterminating process.
Cytotoxic T cells induce apoptosis via two mechanisms: (1) the release of perforin or similar molecules or (2) Fas-mediated cell-to-cell interaction. The release of perforin, granzymes, and granulysin triggers a caspase cascade in target cells, leading to apoptosis. In other cases, the cytotoxic T cell will express the protein Fas ligand, which binds to the fas-receptor on the target cell. This invasion of the target cell induces apoptosis. CD8+ T cells comprise 30% of the Pan T cells in our blood and tissues.
All cells express both internal and external markers that can be used to identify their subset. These markers are found in the form of proteins and glycoproteins and are often given the abbreviation CD, or cluster of differentiation. Each has a specialized role that defines the identity and function of that cell. Surface receptors, along with other cell markers, can be used to identify T cell subtypes from one another and from other cells.
T cells express surface receptors unique to their functions and abilities, but there is one surface marker that is expressed on all T cells, CD3. CD3 is a member of the immunoglobulin superfamily, a protein complex, and functions as a co-receptor on all T cells. Present at every stage of T cell development—even before unassigned T cells enter the thymus—CD3 is used to broadly identify T cells.
CD3 is originally found within the immature T cell as an internal marker and is lost as T cell maturation progresses. Once the expression of CD3 is lost internally, the CD3 antigen can be found on the surface of mature T cells.
The stage in which CD3 is expressed on a T cell can indicate its age and health. This distinction is valuable because a build-up of immature T cells in an area of inflammation can indicate lymphoma or leukemia, as well as identify coeliac disease, type 1 diabetes, and other autoimmune disorders.
Understanding which cell markers are expressed on specific T cell subsets also allows further study of the subtypes’ functions and how they can be utilized in cell therapy research.
Utilizing a column-free and magnet-free kit, Akadeum’s microbubbles are the clear choice for Human T cell isolation and targeting. Our microbubble technology is useful whether you want to isolate a solution enriched with only Pan T cells, target and separate a subset of T cells, or need to remove unwanted T cells from human peripheral blood mononuclear cells (PBMCs) or leukopaks.
Akadeum offers T Cell isolation kits for every experimental need and can provide seamless cell separation of naive T cells and CD4+ T cells from both human and mouse species. Using antibodies to target CD markers expressed on the surface of cells, our microbubbles bind to unwanted cells and simply float to the top of the solution to be aspirated. This results in a pure solution of the T cells of interest, preparing you to seamlessly move to the next workflow stage.
You can also use our microbubbles for cell therapy protocols that require one or multiple T cell subtypes, as is common in cancer and autoimmunity research.
Browse our line of available T Cell Isolation Kits and Solutions to explore how Akadeum microbubbles gently sort cells to improve your research efficiency.