Pan T Cell Antigens and Isolation
Human Pan T Cells
Human Pan T cells are components of the adaptive immune system. They coordinate immune responses to pathogens or tumors.
Pan T cells are the most abundant type of cells among isolated peripheral blood mononuclear cells (PBMCs), representing between 45-70% of total PBMCs.
Pan T cells can discriminate between foreign antigens and self-antigens. The ability to distinguish between healthy cells and those with foreign antigens allows Pan T cells to ignore healthy cells while driving an immune response against cells expressing foreign antigens.
What Are Pan T Cells?
Pan T cells is a term used to describe the totality of T cells and T cell subsets present, including T helper cells (CD4+), regulatory T cells (CD4+CD25+CD127-), cytotoxic T cells and (CD8+), and other subtypes. T-cell progenitors originate from bone marrow as undifferentiated cells. These precursors migrate to the thymus, where they develop into T lymphocytes. During a selection process, T cells mature into the T helper and cytotoxic subtypes. These mature T cells will remain in a naive state until they are needed as part of an immune response. Subsequently, T cells exit the thymus into the periphery where they circulate between the blood and lymphatic system until they encounter their specific antigen. This will activate the effector functions of the T cells, and an immune response will be launched.
Identifying Pan T Cells
Pan T cells are distinguished from other lymphocytes by the presence of T cell receptors (TCRs) on their surface. However, there are multiple T cell subsets, each with specific markers.
Pan T Cell Subtypes
Pan T cells are classified into several different subsets. Each subset can be identified by various internal and external markers, glycoproteins, or lipids, called clusters of differentiation (CD).
CD3+ Pan T Cell Antigen
The CD3 marker is present in all conventional Pan T cells. CD3 serves as a co-receptor for the TCR on the surface of mature T cells. Because CD3 is present through all later stages of T cell development, it is often used to identify Pan T cells.
CD4+ Helper T Cells
CD4+ helper cells make up over 60% of Pan T cells and are characterized by the presence of the CD4 marker.CD4+ helper cells are activated by interactions with antigen-major histocompatibility complex (MHC) II. Upon activation, they differentiate into different subsets. Each subset secretes a different combination of cytokines. Once the infection is gone, most CD4+ helper T cells die, while some become memory T cells. Depending on the subset of the memory T cells, they can reside in secondary lymphoid and non-lymphoid tissues or circulate in the blood.
CD8+ Cytotoxic T Cells
CD8+ cytotoxic cells are a subset of Pan T cells characterized by the CD8 marker. CD8+ cytotoxic cells are a significant population of immune cells in blood and tissues, comprising 30% of Pan T cells. Their role is to induce apoptosis and programmed cell death, in infected, cancerous, or damaged cells.
CD8+ cytotoxic T cells get activated after recognizing peptide antigens bound to the MHC I. Once the infection is cleared, some CD8+ T cells stay as tissue-resident-memory CD8+ T cells.
CD4+, CD25+, and FOXP3+ Regulatory T Cells
CD4+, CD25+, and FOXP3+ regulatory cells are characterized by the expression of CD4+, CD25+, and the transcription factor FOXP3. Their primary role is to modulate immune responses. They also play a role in suppressing autoreactive T cells.
Unconventional T Cells
Unconventional Pan T cells contain several T cell subtypes: γ/δ T cells, natural killer T (NKT) cells, and double-negative T cells.
γ/δ T cells are involved in responding to pathogens and tumors and can be found in the blood, liver, spleen, and thymus, and in the epithelial tissues of the skin, lungs, intestine, and reproductive tract. Activation of γ/δ T cells involves triggering the γδ TCR and recognition of antigens without the presence of MHC molecules.
NKT cells are a unique subset of Pan T cells. Rather than recognizing peptide antigens presented on MHC molecules, these cells are activated by glycolipids presented on CD1d molecules. Precursor and immature natural killer (NK) cells reside in the lymph nodes and intestines, while mature NK cells can be found in the blood, bone marrow, spleen, and lungs.
Double-negative T cells have innate and adaptive immune functions. The term double-negative refers to the lack of both CD4 and CD8 markers on these T cells. Their TCR can be composed of either the conventional α/β or unconventional γ/δ molecules. Double-negative T cells are found in the blood, secondary lymphoid organs, and various tissues, including the intestine, liver, lungs, skin, and genital tract.
Pan T Cell Isolation With BACS™
Many experiments require the isolation of specific subtypes of Pan T cells. Akadeum Life Sciences developed a Pan T cell sorting process— using their patented Buoyancy-Activated Cell Sorting (BACS™)—that employs buoyant microbubbles. Akadeum’s microbubbles are gas-filled microspheres made of a silica shell coated with target-specific affinity molecules.
The isolation process starts with mixing microbubbles with the cell sample where affinity molecules attach to the target cells. Because the microbubbles are less dense than the liquid, they lift the attached cells to the surface of the sample. In the next step, microbubbles, together with the attached cells, can be removed, leaving only the cells of interest for further processing.
Compared to other cell separation methods, such as fluorescence-activated cell sorting (FACS), density centrifugation, or magnetic bead-based cell sorting, isolating a subset of Pan T cells using BACS™ is faster, doesn’t require complex equipment, and is more gentle on the cells.
Check Out Our T Cell Isolation Resources
Akadeum offers a wide selection of buoyant microbubble cell separation products designed for Pan T cell isolation.
You can read Akadeum’s resources regarding cell separation technologies to learn more. If you want to learn specifically about microbubble technology, we recommend reading The Ultimate Guide to Microbubble Technology and Cell Separation.