A naive T cell or Th0 cell^[1] is a T cell that has differentiated in bone marrow, and successfully undergone the positive and negative processes of central selection in the thymus. T cells belong to a group of White blood cells known as Lymphocytes, and play a central role in Cell-mediated immunity. Bone marrow is the flexible tissue found in the hollow interior of Bones In adults marrow in large bones produces new Blood cells It constitutes 4% of Central tolerance is the mechanism by which newly developing T cells and B cells are rendered non-reactive to self In Human anatomy, the thymus is an organ located in the upper Anterior portion of the chest cavity just behind the Sternum. A naive T cell is considered mature, but is distinguished from activated T cells or memory T cells, as it is thought not to have yet encountered cognate antigen in the periphery. Memory T cells are a specific type of Infection -fighting T cell (also known as a T lymphocyte) that can recognize foreign invaders such as Bacteria An antigen (from antibody-generating) or immunogen is a substance that prompts the generation of Antibodies and can cause an immune response

Naive T cells are commonly characterized by the surface expression of L-selectin (CD62L); the absence of the activation markers CD25, CD44 or CD69; and the absence of memory markers, such as the edited CD45 isoforms. L-selectin, also known as CD62L, is a Cell adhesion molecule found on Leukocytes. L-selectin, also known as CD62L, is a Cell adhesion molecule found on Leukocytes. The interleukin-2 receptor (IL-2R is heterotrimeric protein expressed on the surface of certain immune cells such as Lymphocytes that binds and responds to The CD44 Protein is a cell -surface Glycoprotein involved in cell-cell interactions cell adhesion and migration CD69 ( C luster of D ifferentiation 69 is a human Protein encoded by the Gene. In Immunology, the CD45 Antigen (CD stands for Cluster of differentiation) is a Protein which was originally called leukocyte common antigen In the naive state, T cells are thought to be quiescent and non-dividing, requiring the common-gamma chain cytokines IL-7 and IL-15 for homeostatic survival. Interleukin 7 ( IL7) is a hematopoietic Growth factor secreted by the stromal cells of the red marrow and thymus capable of stimulating the proliferation of Lymphoid

Naive T cells are able to respond to novel pathogens that the immune system has not yet encountered. A pathogen (from Greek πάθος pathos "suffering passion" and γἰγνομαι (γεν- gignomai (gen- "I give birth to" infectious Recognition by a naive T cell clone of its cognate antigen results in the initiation of an acquired immune response. Immune system|Passive immunity|Innate immune system The adaptive immune system is composed of highly specialized systemic cells and processes that eliminate or prevent Pathogenic In the ensuing response, the T cell acquires an activated phenotype (CD25⁺, CD44⁺, CD62L^low, CD69⁺), and may further differentiate into a memory T cell. Memory T cells are a specific type of Infection -fighting T cell (also known as a T lymphocyte) that can recognize foreign invaders such as Bacteria

Having adequate numbers of naive T cells is essential to an immune system for it to be able to adapt to new pathogens experienced in life. As there are a limited number of T-cells in the body, eventually the amount can be taken up by memory cells for pathogens encountered in the past that may no longer be needed in comparison to more widely spread modern strains of pathogens.

See also

• Immune system
• Memory T cells

References

---

© 2009 citizendia.org; parts available under the terms of GNU Free Documentation License, from http://en.wikipedia.org
Dapyx Software network: MP3 Explorer | Ebook Manager | Zenithic