Bakouche O, Brown D C, Lachman L B
J Immunol. 1987 Jun 15;138(12):4249-55.
IL 1 activity, as assayed by the proliferation of responsive mouse thymocytes and a human astrocytoma cell line, was detected on the membrane of 1% paraformaldehyde-fixed activated human monocytes. Resting, unactivated monocytes did not display IL 1 activity. Maximum induction of membrane IL 1 was obtained from monocytes treated with polyclonal activators, such as LPS or Staphylococcus aureus, whereas adherence was a weak inducer of membrane IL 1. Isolated cell compartments as plasma membranes, crude lysosomes, and crude cytosol from activated human monocytes expressed significant IL 1 activity, whereas the endoplasmic reticulum showed no IL 1 activity. Exposure to trypsin of either fixed, activated human monocytes or cell compartments from unfixed monocytes, revealed biologically active IL 1 in the membrane, crude lysosome, and crude cytosol, but not in the endoplasmic reticulum. The IL 1 activity in the purified cytosol, prepared by extraction with digitonin, was considerably increased by the trypsin treatment, whereas the increase in IL 1 activity within crude lysosomes and plasma membranes was less. The cell compartments from nonactivated monocytes did not express active IL 1 and trypsin treatment revealed no active IL 1, suggesting the absence of a pool of the trypsin-sensitive form of IL 1. The data confirm the presence of membrane-bound IL 1 in activated human monocytes and indicate that an inactive precursor molecule can be found in the cytosol of such cells. Furthermore, the absence of IL 1 activity either in its active form or as the inactive precursor in the endoplasmic reticulum suggests that IL 1 is not a conventionally secreted protein. Because IL 1 was found in the cytosol as a precursor and in the lysosomal fractions in an active form, these data suggest that after the synthesis and processing of the cytosolic precursor, the 17-kda IL 1, is released via lysosomal vesicles.
通过反应性小鼠胸腺细胞和人星形细胞瘤细胞系的增殖来测定白细胞介素1（IL 1）活性，结果在1%多聚甲醛固定的活化人单核细胞膜上检测到了该活性。静止、未活化的单核细胞未显示出IL 1活性。用多克隆激活剂（如脂多糖或金黄色葡萄球菌）处理单核细胞可获得膜IL 1的最大诱导量，而黏附是膜IL 1的较弱诱导剂。从活化的人单核细胞分离出的细胞膜、粗溶酶体和粗胞质溶胶等细胞区室表现出显著的IL 1活性，而内质网未显示出IL 1活性。用胰蛋白酶处理固定的活化人单核细胞或未固定单核细胞的细胞区室后，在细胞膜、粗溶酶体和粗胞质溶胶中发现了具有生物活性的IL 1，但在内质网中未发现。用洋地黄皂苷提取制备的纯化胞质溶胶中的IL 1活性经胰蛋白酶处理后显著增加，而粗溶酶体和细胞膜中IL 1活性的增加较少。未活化单核细胞的细胞区室不表达活性IL 1，胰蛋白酶处理也未显示出活性IL 1，这表明不存在胰蛋白酶敏感形式的IL 1库。这些数据证实了活化的人单核细胞中存在膜结合的IL 1，并表明在这类细胞的胞质溶胶中可发现一种无活性的前体分子。此外，内质网中既不存在活性形式的IL 1，也不存在无活性前体形式的IL 1，这表明IL 1不是一种传统分泌蛋白。由于在胞质溶胶中发现IL 1以前体形式存在，而在溶酶体组分中以活性形式存在，这些数据表明，在胞质前体合成和加工后，17 kDa的IL 1通过溶酶体小泡释放。
