Specialization of the macrophage plasma membrane at sites of interaction with opsonized erythrocytes.

We incubated mouse peritoneal macrophages for 3-8 min at 37 degrees C with antibody-coated sheep erythrocytes and examined regions of close interaction between the two cell types by electron microscopy. At sites of focal macrophage-erythrocyte contact we observed a distinctive specialization of the macrophage plasma membrane consisting of a prominent subplasmalemmal band of electron-dense material, approximately 25-35 nm in thickness. In many instances, this band showed a periodic substructure similar to that seen in clathrin coats. Moreover, many slender erythrocyte processes penetrated into invaginations of the macrophage surface which were bristle-coated at their blind extremity. As previously shown for clathrin-coated pits, the segments of the macrophage plasma membrane beneath which the defense material was found were selectively resistant to the membrane-perturbing effect of the antibiotic, filipin. This structural specialization of the macrophage plasma membrane at sites of ligand-receptor interaction during immune phagocytosis of antibody-coated erythrocytes may represent the morphological counterpart of the zipper mechanism of phagocytosis previously demonstrated by functional studies.

Leukocyte interleukins induce cultured endothelial cells to produce a highly organized, glycosaminoglycan-rich pericellular matrix.

We report here that interleukins have a dramatic effect on extracellular matrix production by cultured endothelial cells. Human umbilical vein endothelial cells incubated with growth media conditioned by lectin-activated human peripheral blood mononuclear leukocytes undergo marked changes in cell shape and elaborate a highly organized extracellular material that is not detectable in untreated cultures. This material has the following characteristics: (a) it is not recognizable by electron microscopy unless the cationic dye, Alcian blue, is added to the fixative; (b) it is visualized as a network of branching and anastomosing fibrils of various thickness that can be resolved into bundles of fine filaments; (c) it is associated with the cell surface, extends between contiguous cells, and coats the culture substrate; (d) it is removed by digestion with glycosaminoglycan-degrading enzymes, such as crude heparinase and chondroitinase ABC. These results demonstrate that soluble factors released by activated peripheral blood mononuclear leukocytes (interleukins) stimulate cultured human umbilical vein endothelial cells to produce a highly structured pericellular matrix containing glycosaminoglycans (probably chondroitin sulfate and/or hyaluronic acid) as a major constituent. We speculate that this phenomenon corresponds to an early step of angiogenesis as observed in vivo as a consequence of interleukin release.

Postoperative chylothorax in children: differences between vascular and traumatic origin.

Twenty-four children with postoperative chylothorax were encountered among 1,264 consecutive thoracic operations over a 7-year period and form the basis of this study. Chylothorax was caused by direct lesion to the thoracic duct or lymphatic vessels in 17 patients and was associated with superior vena cava (SVC) obstruction in seven. Of the latter, five had bilateral chylothorax. Chylothoraces secondary to venous hypertension and thrombosis have a longer interval between operation and diagnosis compared with direct trauma as well as a longer duration and larger volume of chylous drainage. Treatment was entirely nonoperative in 16 patients and operative in 8. Nonoperative treatment consisted of pleural needle aspiration or suction drainage in association with a medium chain triglyceride (MCT) diet (n = 11) or total parenteral nutrition (TPN) after failure of MCT (n = 5). Direct operation on the thoracic duct was performed in 5 patients, four had pleurodesis, and 2 had pleuroperitoneal shunts inserted. All patients were cured of their chylothorax and there were no deaths. Patients with major vein thrombosis were the most difficult to treat. On the basis of this experience, we suggest a step-by-step approach: (1) insertion of chest tube after 3 to 4 pleural punctures; (2) 1-week trial of MCT diet, with intravenous support to correct protein losses; (3) TPN if chylothorax increases or persists with large volumes; (4) Doppler echocardiography or phlebography to rule out obstruction of major thoracic veins; and (5) insertion of TPN line in inferior vena cava in case of such obstruction; and (6) direct surgical approach to the thoracic duct after 4 weeks of unsuccessful nonoperative treatment.(ABSTRACT TRUNCATED AT 250 WORDS)