Kuis W, Villiger P M, Leser H G, Lotz M
Department of Molecular and Experimental Medicine, Research Institute of Scripps Clinic, La Jolla, California 92037.
J Clin Invest. 1991 Sep;88(3):817-24. doi: 10.1172/JCI115382.
Human peripheral blood mononuclear cells are analyzed for preproenkephalin gene expression and peptide processing. Met-enkephalin immunoreactivity as detected with a specific antiserum is found in the cytoplasm of monocytes but not in T lymphocytes. Secretion of met-enkephalin was analyzed with an RIA that is specific for the met-enkephalin pentapeptide. Unfractionated PBMC spontaneously released 40 pg/ml met-enkephalin and this increased two- to fourfold after stimulation with PHA. Lower levels (less than 100 pg/ml) of met-enkephalin were detected in supernatants from purified T cells that were activated with PHA and IL-2. In contrast, stimulation of purified monocytes with LPS or PMA resulted in the release of up to 600 pg/ml of the processed peptide. To examine whether T cells can produce met-enkephalin precursor peptides, T cell conditioned media were treated with trypsin and carboxypeptidase-B, which is known to release met-enkephalin from the propeptide. This increased levels of met-enkephalin to 400 pg/ml, indicating that lymphocytes secrete the propeptide but do not process it to met-enkephalin. The 1.4-kb preproenkephalin mRNA is detected in activated blood mononuclear cells and in purified monocytes and T cells. To determine whether monocytes or lymphocytes express met-enkephalin in vivo, lymphoid tissues were analyzed by immunohistochemistry. In human spleen tissue, positive cells were found in the red pulp but not in the follicles, which is also consistent with met-enkephalin expression in monocytes. In summary, these results show that human peripheral blood mononuclear cells express preproenkephalin mRNA and that monocytes, but not T cells, process the propeptide to metenkephalin.
对人外周血单个核细胞进行前脑啡肽原基因表达和肽加工分析。用特异性抗血清检测到的甲硫氨酸脑啡肽免疫反应性存在于单核细胞的细胞质中，而不存在于T淋巴细胞中。用对甲硫氨酸脑啡肽五肽特异的放射免疫分析法分析甲硫氨酸脑啡肽的分泌。未分级的外周血单个核细胞自发释放40 pg/ml甲硫氨酸脑啡肽，用PHA刺激后增加2至4倍。在用PHA和IL-2激活的纯化T细胞的上清液中检测到较低水平（低于100 pg/ml）的甲硫氨酸脑啡肽。相反，用LPS或PMA刺激纯化的单核细胞会导致释放高达600 pg/ml的加工后肽。为了检查T细胞是否能产生甲硫氨酸脑啡肽前体肽，用胰蛋白酶和羧肽酶B处理T细胞条件培养基，已知这两种酶能从前体肽中释放甲硫氨酸脑啡肽。这使甲硫氨酸脑啡肽水平增加到400 pg/ml，表明淋巴细胞分泌前体肽但不将其加工成甲硫氨酸脑啡肽。在活化的血液单个核细胞以及纯化的单核细胞和T细胞中检测到1.4 kb的前脑啡肽原mRNA。为了确定单核细胞或淋巴细胞在体内是否表达甲硫氨酸脑啡肽，通过免疫组织化学分析淋巴组织。在人脾组织中，在红髓中发现阳性细胞，而在滤泡中未发现，这也与单核细胞中甲硫氨酸脑啡肽的表达一致。总之，这些结果表明人外周血单个核细胞表达前脑啡肽原mRNA，并且单核细胞而非T细胞将前体肽加工成甲硫氨酸脑啡肽。
