CD99 is expressed on all leukocytes (the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders) but highest on thymocytes and is believed to augment T-cell adhesion and apoptosis of double positive T cells, and has been found in endothelial cells and in the periodontium, including gingival fibroblasts and gingival epithelial cells.
It is expressed on all leukocytes but highest on thymocytes and is believed to augment T-cell adhesion and apoptosis of double positive T cells. It has been found in endothelial cells and in the periodontium, including gingival fibroblasts and gingival epithelial cells. White blood cells (WBCs), also called leukocytes or leucocytes, are the cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. 
