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The thymus (pl.: thymuses or thymi) is a specialized primary lymphoid organ of the immune system.Within the thymus, thymus cell lymphocytes or T cells mature. T cells are critical to the adaptive immune system, where the body adapts to specific foreign invaders.
Thymocytes are classified into a number of distinct maturational stages based on the expression of cell surface markers. The earliest thymocyte stage is the double negative stage (negative for both CD4 and CD8), which more recently has been better described as Lineage-negative, and which can be divided into four substages.
The hypothalamus, pancreas, and thymus also function as endocrine glands, among other functions. (The hypothalamus and pituitary glands are organs of the neuroendocrine system . One of the most important functions of the hypothalamus—it is located in the brain adjacent to the pituitary gland—is to link the endocrine system to the nervous ...
Thymus stromal cells are subsets of specialized cells located in different areas of the thymus. [1] They include all non-T-lineage cells, such as thymic epithelial cells (TECs), endothelial cells, mesenchymal cells, dendritic cells, and B lymphocytes, and provide signals essential for thymocyte development and the homeostasis of the thymic stroma.
Major function of cTECs is to positively select those T cells that are capable to recognize and interact with MHC molecules on their surface [3]. Once T cell precursors enter the thymic cortex, they start their transformation from double negative stages (T cell without surface expression of CD4 and CD8 co-receptors) to a double positive stage (T cell with surface expression of both co ...
The thymus contributes fewer cells as a person ages. As the thymus shrinks by about 3% [15] a year throughout middle age, a corresponding fall in the thymic production of naive T cells occurs, leaving peripheral T cell expansion and regeneration to play a greater role in protecting older people.
The thymus gland cells form part of the body's immune system. In those with myasthenia gravis, the thymus gland is large and abnormal. It sometimes contains clusters of immune cells that indicate lymphoid hyperplasia, and the thymus gland may give wrong instructions to immune cells.
An X-ray of a human chest area, with some structures labeled. The contents of the thorax include the heart and lungs (and the thymus gland); the major and minor pectoral muscles, trapezius muscles, and neck muscle; and internal structures such as the diaphragm, the esophagus, the trachea, and a part of the sternum known as the xiphoid process.