分化 (CD) 抗原簇是一種(zhong)用于識別和(he)研究白細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)上(shang)存在的(de)細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)表(biao)面分子(zi)的(de)方(fang)案(an)。一些 CD 蛋白通(tong)常(chang)充當細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)-細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)或細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)-基質(zhi)粘附分子(zi)、細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)因子(zi)受體(ti)(ti)、離子(zi)孔(kong)或營養轉運蛋白。 CD 蛋白在免疫系(xi)統(tong)功能中(zhong)發揮多種(zhong)作用。 T 細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)的(de)譜(pu)系(xi)特異性(xing)標記是細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)質(zhi) CD3，它作為胸腺(xian)(xian)中(zhong)的(de)前(qian)(qian)體(ti)(ti)出(chu)現在最早的(de) T 細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)中(zhong)。早期 T 細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)前(qian)(qian)體(ti)(ti)也(ye)表(biao)達 CD2 和(he) CD7。在胸腺(xian)(xian)成(cheng)熟過程中(zhong)，T 細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)前(qian)(qian)體(ti)(ti)經歷 T 細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)受體(ti)(ti)的(de)重排。這(zhe)一過程伴(ban)隨著其他 T 細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)譜(pu)系(xi)相關標記（CD5、CD4、CD8）的(de)出(chu)現。大(da)多數(shu)成(cheng)熟 T 細(xi)(xi)(xi)(xi)(xi)(xi)(xi)胞(bao)是 CD4⁺或CD8⁺。然而，胸腺細(xi)(xi)(xi)胞和(he)異常腫(zhong)瘤性 T 細(xi)(xi)(xi)胞可能共(gong)表達 CD4 和(he) CD8 以及未成熟 T 細(xi)(xi)(xi)胞標(biao)記物 TdT 和(he) CD1a。