The immune system is composed of a diverse array of cells and tissues that work together to protect the body from infections and other threats. Here are some of the key cells and tissues of the immune system:
- Bone marrow: The bone marrow is the site of hematopoiesis, where hematopoietic stem cells differentiate into various types of blood cells, including leukocytes that are involved in immune function.
- Thymus: The thymus is a gland located in the upper chest that plays a critical role in T cell maturation and differentiation. Immature T cells migrate from the bone marrow to the thymus, where they undergo positive and negative selection to ensure that only T cells with appropriate antigen specificity and self-tolerance survive.
- Lymph nodes: Lymph nodes are small, bean-shaped structures located throughout the body that are involved in filtering lymphatic fluid and providing a site for immune cell activation and proliferation. Lymph nodes contain various immune cells, including B cells, T cells, and antigen-presenting cells.
- Spleen: The spleen is a large organ located in the upper left side of the abdomen that filters blood and removes damaged or old blood cells. The spleen also provides a site for immune cell activation and proliferation and contains various immune cells, including B cells, T cells, and antigen-presenting cells.
- Mucosal-associated lymphoid tissue (MALT): MALT is a network of lymphoid tissue located in various mucosal surfaces throughout the body, including the respiratory, gastrointestinal, and urogenital tracts. MALT contains immune cells that can provide a first line of defense against infectious agents that enter the body through these surfaces.
- Skin-associated lymphoid tissue (SALT): SALT is a network of lymphoid tissue located in the skin that contains immune cells, including dendritic cells, macrophages, and T cells. SALT can provide a first line of defense against pathogens that enter the body through the skin.
- Blood: Blood contains various types of immune cells, including leukocytes that are involved in immune function. Immune cells can circulate in the blood and migrate to sites of infection or inflammation.
These are just some of the key cells and tissues of the immune system. The immune system is a highly complex and dynamic system that involves many other cell types, tissues, and interactions.