Chambers J D, Simon S I, Berger E M, Sklar L A, Arfors K E
La Jolla Institute for Experimental Medicine, California 92037.
J Leukoc Biol. 1993 Apr;53(4):462-9. doi: 10.1002/jlb.53.4.462.
Flow cytometry and fluorescently labeled monoclonal antibodies were used to investigate endocytosis of human neutrophil beta 2 integrins following cellular activation. CD18 initially present on the cell surface cycled in two phases after exposure to formyl peptide or platelet-activating factor. The first phase lasted 3 min at 37 degrees C; after a lag, CD18 was specifically internalized at approximately 20%/min. Subsequently a second phase was detectable consisting of exponential reduction of internal fluorescence with a half-time of approximately 2 min, representing probe reexpression. At peak endocytosis approximately 40% of CD18 was internalized. All of the internalized CD18 was associated with alpha M (CR3); no endocytosis of alpha L (LFA-1) was observed. When neutrophils were stimulated with phorbol esters or calcium ionophore, CD18 was internalized much more slowly (t1/2 = 5 min) and probe was not reexpressed. Endocytosis of CD18 may participate in regulating neutrophil adhesiveness, removing activated receptors, or permitting receptor recycling.
采用流式细胞术和荧光标记单克隆抗体，研究细胞活化后人中性粒细胞β2整合素的内吞作用。暴露于甲酰肽或血小板活化因子后，最初存在于细胞表面的CD18以两个阶段循环。第一阶段在37℃持续3分钟；经过一段延迟后，CD18以约20%/分钟的速率特异性内化。随后可检测到第二阶段，表现为内部荧光呈指数下降，半衰期约为2分钟，代表探针重新表达。在内吞作用高峰期，约40%的CD18被内化。所有内化的CD18均与αM（CR3）相关；未观察到αL（LFA-1）的内吞作用。当中性粒细胞用佛波酯或钙离子载体刺激时，CD18内化要慢得多（t1/2 = 5分钟），且探针未重新表达。CD18的内吞作用可能参与调节中性粒细胞黏附性、去除活化受体或允许受体循环利用。
