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Follicular helper T cells (also known as T follicular helper cells and abbreviated as T FH), are antigen-experienced CD4 + T cells found in the periphery within B cell follicles of secondary lymphoid organs such as lymph nodes, spleen and Peyer's patches, and are identified by their constitutive expression of the B cell follicle homing receptor CXCR5. [1]
T cells are one of the important types of white blood cells of the immune system and play a central role in the adaptive immune response. T cells can be distinguished from other lymphocytes by the presence of a T-cell receptor (TCR) on their cell surface. T cells are born from hematopoietic stem cells, [1] found in the bone marrow.
The T helper cells (T h cells), also known as CD4 + cells or CD4-positive cells, are a type of T cell that play an important role in the adaptive immune system. They aid the activity of other immune cells by releasing cytokines .
Subsequently, the primed cells will differentiate either into effector cells or into memory cells that can mount stronger and faster response to second and upcoming immune challenges. [2] T and B cell priming occurs in the secondary lymphoid organs (lymph nodes and spleen). Priming of naïve T cells requires dendritic cell antigen presentation.
Antigen presentation is a vital immune process that is essential for T cell immune response triggering. Because T cells recognize only fragmented antigens displayed on cell surfaces, antigen processing must occur before the antigen fragment can be recognized by a T-cell receptor.
This discovery furthered the development of a previously hypothesized theory, the immunosurveillance theory. The immunosurveillance theory suggests that the immune system routinely patrols the cells of the body, and, upon recognition of a cell, or group of cells, that has become cancerous, it will attempt to destroy them, thus preventing the growth of some tumors.
In central tolerance, dendritic cells are present within the thymus, or the location of T cell development and maturation. Thymic dendritic cells can intake dead medullary thymic epithelial cells, and cross present "self" peptides on MHC class I as a negative selection check on cytotoxic T cells that have a high affinity for self peptides. [6]
All T cells derive from progenitor cells in the bone marrow, which become committed to their lineage in the thymus.All T cells begin as CD4-CD8-TCR- cells at the DN (double-negative) stage, where an individual cell will rearrange its T cell receptor genes to form a unique, functional molecule, which they, in turn, test against cells in the thymic cortex for a minimal level of interaction with ...