Periarteriolar lymphoid sheaths

Periarteriolar Lymphoid Sheaths

File:Periarteriolar lymphoid sheaths.jpg

Illustration of Periarteriolar Lymphoid Sheaths

The Periarteriolar Lymphoid Sheaths (PALS) are a distinctive feature of the spleen's white pulp, which is a part of the immune system. They are primarily composed of T cells and are located around the central arterioles within the spleen.

Structure

The PALS are cylindrical structures that surround the central arterioles in the spleen. They are primarily composed of T cells, but also contain other immune cells such as B cells, macrophages, and dendritic cells. The PALS are separated from the red pulp of the spleen by the marginal zone, which is a region rich in B cells, macrophages, and dendritic cells.

Function

The primary function of the PALS is to provide a site for the activation of T cells. When an antigen enters the spleen, it is captured by dendritic cells in the marginal zone. These dendritic cells then migrate to the PALS, where they present the antigen to T cells. This leads to the activation of the T cells, which then proliferate and differentiate into effector T cells.

Clinical Significance

Abnormalities in the structure or function of the PALS can lead to a variety of immune disorders. For example, in autoimmune diseases, the PALS may become hyperactive, leading to the destruction of self-tissues. Conversely, in immunodeficiency diseases, the PALS may be underactive, leading to an inability to fight off infections.

See Also

• Spleen
• T cells
• B cells
• Dendritic cells
• Macrophages