图示：胎儿胸腺中T淋巴细胞退化就是细胞凋亡的结果。单个细胞的碎片化和吞噬细胞吞噬形成了大量的细胞碎片。调亡的调控机制非常复杂。Bcl-2基因抑制凋亡，Bax基因促进凋亡。称为Caspases酶的蛋白水解酶促使细胞破坏。
In this fetal thymus there is involution of thymic lymphocytes by the mechanism of apoptosis. In this case, it is an orderly process and part of normal immune system maturation. Individual cells fragment and are consumed by phagocytes to give the appearance of clear spaces filled with cellular debris. Apoptosis is controlled by many mechanisms. Genes such as BCL-2 are turned off and Bax genes turned on. Intracellular proteolytic enzymes called caspases produce much cellular breakdown.