Human Peripheral Blood CD4+ T Cells: HPBT

Human Peripheral Blood T Cells (HPBT) play critical roles in the regulation of immune responses, and are responsible for mediating many of the effector mechanisms of the immune system. T cells originate from pluripotent hematopoetic stem cells, and differentiate in thymus and expand by cell division to generate a large population of immature thymocytes. The earliest thymocytes express neither CD4 nor CD8, and are therefore classed as double-negative (CD4-CD8-) cells. As they progress through their development they become double-positive thymocytes (CD4+CD8+), and finally mature to single-positive (CD4+CD8- or CD4-CD8+) thymocytes that are then released from the thymus to peripheral tissues. About 98% of thymocytes die during the development processes in the thymus by failing either positive selection or negative selection, whereas the other 2% survive and leave the thymus to become mature immunocompetent T cells. The thymus contributes more naive T cells at younger ages. As the thymus shrinks by about 3% a year throughout middle age, there is a corresponding fall in the thymic production of naive T cells, leaving peripheral T cell expansion to play a greater role in protecting older subjects.¹

As a major part of the adaptive immune system, T cells scan the intracellular environment in order to target and destroy infected cells. In general, the T cell receptors (TCRs) on the surface of T cells² are responsible for recognizing antigens bound to major histocompatibility complex (MHC) molecules. T cell activation can lead to a number of immune responses such as antibody production, activation of phagocytic cells and direct cell killing. In this way, the appropriate immune response for different types of diseases is implemented.³ Activation of T cells is a key event for an efficient response of the immune system. It requires the involvement of TCR as well as costimulatory molecules such as CD28. Engagement of these receptors through the interaction with a foreign antigen associated with major histocompatibility complex molecules and CD28 counter-receptors B7.1/B7.2, respectively, results in a series of signaling cascades. These cascades comprise an array of protein-tyrosine kinases, phosphatases, GTP-binding proteins and adaptor proteins that regulate generic and specialized functions, leading to T-cell proliferation, cytokine production and differentiation into effector cells.⁴

Human Peripheral Blood CD4+ T Cells (HPBT) should provide a useful tool for studying various aspects of pathology and biology of the human CD4+ T cells in vitro. Moreover, the expansion of the biotechnology industry has led to a dramatic increase in the number of novel immunotherapeutics that are being developed for the treatment of cancer, autoimmune disorders and infectious diseases. This increase in activity in the field of immunotherapy, coupled with the expense of clinical trials, has led to renewed interest in obtaining high purity human T cells. To meet various needs for research and development, Cell Applications, Inc isolated and purified Human Peripheral Blood CD4+ T Cells (HPBT) from human blood of healthy donors to create a more realistic in vitro model. They are cryopreserved immediately after isolation.

1. Reinherz, E.L. et al, Immunol. Today 2:69 (1981)
2. Kindt, T. J. et al, Kuby immunology. Macmillan. p223 (2007)
3. Smith-Garvin, J.E. et al, Annu. Rev. Immunol. 27:591 (2009)
4. Dustin, M.L. Immunity 30:482 (2009)

Characterization:

Each lot tested negative for HIV, Hepatitis B and Hepatitis C and negative for mycoplasma, bacteria, yeast, fungi.
Products are for research use only. They are not intended for human, animal, or diagnostic applications.

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