The blood–thymus barrier regulates exchange of substances between the
circulatory system
In vertebrates, the circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the body. It includes the cardiovascular system, or vascular system, that consists of the heart ...
and
thymus
The thymus (: thymuses or thymi) is a specialized primary lymphoid organ of the immune system. Within the thymus, T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders. The thymus ...
, providing a sequestered environment for immature
T cells
T cells (also known as T lymphocytes) are an important part 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 ce ...
to develop. The barrier also prevents the immature T cells from contacting foreign
antigens
In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response.
An ...
(since contact with antigens at this stage will cause the T cells to die by
apoptosis
Apoptosis (from ) is a form of programmed cell death that occurs in multicellular organisms and in some eukaryotic, single-celled microorganisms such as yeast. Biochemistry, Biochemical events lead to characteristic cell changes (Morphology (biol ...
).
The barrier is formed by the continuous blood capillaries in the thymic cortex, reinforced by type 1 epithelial reticular cells (sometimes called
thymic epithelial cells) and
macrophages
Macrophages (; abbreviated MPhi, φ, MΦ or MP) are a type of white blood cell of the innate immune system that engulf and digest pathogens, such as cancer cells, microbes, cellular debris and foreign substances, which do not have proteins that ...
.
The existence of this barrier was first proposed in 1961 and demonstrated to exist in mice in 1963.
See also
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References
{{DEFAULTSORT:Blood-thymus barrier
Thorax (human anatomy)
Organs (anatomy)