Seibold F, Seibold-Schmid B, Cong Y, Shu F Y, McCabe R P, Weaver C, Elson C O
Department of Medicine, University of Alabama at Birmingham, Birmingham, Alabama 35294-0007, USA.
Gastroenterology. 1998 May;114(5):965-74. doi: 10.1016/s0016-5085(98)70316-6.
BACKGROUND & AIMS: The expression of the lymphocyte homing receptor and activation marker L-selectin is different in colon and small intestinal intraepithelial lymphocytes (IELs). In this study, the mechanism of this difference in L-selectin expression was investigated.
L-selectin expression on lymphocytes was measured by flow cytometry. L-selectin messenger RNA (mRNA) was detected by reverse-transcription polymerase chain reaction. L-Selectin expression on peripheral lymphocytes was analyzed after incubation with cytokines, food and bacterial antigens, and homogenates of small and large bowel.
L-selectin was expressed by none of the small intestinal IELs but by 30% of those in the colon and by 60% of splenocytes. mRNA for L-selectin was detectable in isolated lymphocytes of all three sites. L-Selectin was down-regulated in colon IELs during colitis and up-regulated in small intestinal IELs after in vitro culture for 48 hours. Incubation of splenocytes with small intestinal homogenates led to a rapid down-regulation of L-selectin (1% vs. 60% untreated). Preincubation with a metalloproteinase inhibitor prevented L-selectin loss.
The mechanism of the differential expression of L-selectin in mouse small intestine and colon appears to be an increased functional activity of a metalloproteinase (sheddase) in the small intestine compared with the colon.
淋巴细胞归巢受体及活化标志物L-选择素在结肠和小肠上皮内淋巴细胞（IEL）中的表达存在差异。本研究对L-选择素表达差异的机制进行了探究。
采用流式细胞术检测淋巴细胞上L-选择素的表达。通过逆转录聚合酶链反应检测L-选择素信使核糖核酸（mRNA）。在与细胞因子、食物、细菌抗原以及小肠和大肠匀浆孵育后，分析外周淋巴细胞上L-选择素的表达。
小肠IEL均不表达L-选择素，但结肠IEL中有30%表达，脾细胞中有60%表达。在所有三个部位分离出的淋巴细胞中均可检测到L-选择素的mRNA。在结肠炎期间，结肠IEL中L-选择素表达下调，而在体外培养48小时后，小肠IEL中L-选择素表达上调。脾细胞与小肠匀浆孵育导致L-选择素迅速下调（未处理组为60%，处理组为1%）。用金属蛋白酶抑制剂预孵育可防止L-选择素丢失。
小鼠小肠和结肠中L-选择素差异表达的机制似乎是与结肠相比，小肠中金属蛋白酶（脱落酶）的功能活性增强。
