High endothelial microveins are specialized veins that are found in almost all peripheral lymphoid organs and lymphoid tissues except the spleen, including lymph nodes, tonsils, collecting lymph nodes of the small intestine, and lymph nodes of the appendicitis, stomach, and large intestine. These highly endothelial microvessels, which are specialized channels for lymphocytes to enter from the circulation into lymphoid tissues and lymphoid organs, are primarily used to recruit lymphocytes to accomplish anti-inflammatory effects. In chronic inflammation of non-lymphoid tissues, high endothelial cell microvein-like vessels can also be seen, so the significance of this vein is to allow lymphocytes to enter from the bloodstream into lymphoid tissues or lymphoid organs to complete immunity.