Xiaopu Li

EFFECT OF SHEAR STRESS ON EFFERENT LYMPH-DERIVED LYMPHOCYTES IN CONTACT WITH ACTIVATED ENDOTHELIAL MONOLAYERS

SummaryLymphocyte interactions with endothelial cells in microcirculation are an important regulatory step in the delivery of lymphocytes to peripheral sites of inflammation. In normal circumstances, the predicted wall shear stress in small venules range from 10 to 100 dyn/cm2. Attempts to measure the adhesion of lymphocytes under physiologic conditions have produced variable results, suggesting the importance of studying biologically relevant migratory lymphocytes. To quantify the effect of shear stress on these migratory lymphocytes, we used lymphocytes obtained from sheep efferent lymph ducts, defined as migratory cells, to perfuse sheep endothelial monolayers under conditions of flow. Quantitative cytomorphometry was used to distinguish cells in contact with the endothelial monolayers from cells in the flow stream. As expected, migratory cells in contact with the normal endothelial monolayer demonstrated flow velocities less than the velocity of cells in the adjacent flow stream. The flow velocities of these efferent lymphocytes were independent of cell size. To model the inflammatory microcirculation, lymphocytes were perfused over sequential endothelial monolayers to directly compare the velocity of cells in contact with cytokine-activated and unactivated control monolayers. The tumor necrosis factor and interleukin-1-activated endothelial monolayers marginally decreased cell velocities at 1.2 dyn/cm2 (3.6%), but significantly reduced cell velocities 0.3 dyn/cm2 (27.4%; P<0.05). Similarly, the fraction of statically adherent lymphocytes decreased as shear stress increased to 1.2 dyn/cm2. These results suggest that typical wall shear stress in small venules, of the order of 20 dyn/cm2, are too high to permit adhesion and transmigration of migratory lymphocytes. Additional mechanisms must be present in vivo to facilitate lymphocyte transmigration in the inflammatory microcirculation.

In situ fluorescence labeling of sheep lung microvascular endothelium

SummaryEndothelial cells are intimately involved in a variety of biological processes such as inflammatory disorders, wound healing, and tumor invasion. The finding of endothelial heterogeneity in various tissues has led to major efforts to isolate and culture microvascular endothelial cells in human and animal tissue. In this report we have used phosphatidyl ethanolamine (PE)-labeled liposomes to fluorescently label the sheep lung microvasculature in situ. Using normotensive perfusion pressure, the PE-labeled liposomes did not extravasate into extravascular lung tissue. Mechanical and enzymatic digestion of the lung tissue demonstrated that the PE-labeled liposomes provided a stable label of the vascular lining cells during ex vivo processing. After digestion, the overwhelming majority of the fluorescent label appeared in cellular aggregates. Approximately 80% of these cells demonstrated an in vitro phenotype consistent with microvascular endothelium. A novel monoclonal antibody selective for sheep endothelial cells was developed to confirm the presence of lung endothelium in the fluorescently labeled cellular aggregates. We conclude that in situ fluorescence labeling of vascular lining cells provides an anatomic marker for relevant vascular lining cells and an opportunity to study these cells in vitro.

o-phthaldehyde fluorescence microassay for the determination of antibody concentration.

o-Phthaldehyde (OPA) reagent reacts with primary amines in aqueous solution at room temperature. When the reaction occurs in the presence of 2-mercaptoethanol, a bright blue fluorescence is produced. We investigated the application of the OPA reagent in the routine determination of monoclonal antibody concentration. The OPA reagent produced maximal fluorescence within 30 min and was stable for 2 h. Buffers containing primary amines gave high background fluorescence; however, the OPA reagent gave reliable results with the most commonly used antibody solutions. The OPA reagent provided a rapid and simple measure of protein concentration from 1 microgram to 1 mg and was readily adapted for use with a 96-well fluorescence reader.

Membrane glycoconjugates expressed on sheep airway epithelium.

In mammalian lung, selective airway inflammatory reactions have been associated with viral infections, transplant rejection, and autoimmune diseases. Although the molecular basis for this selective reactivity is unknown, the importance of carbohydrates in immunologic processes suggests a potential role for membrane glycoconjugates in tissue-specific inflammatory reactions. In the present work we examined a panel of 39 lectins for their pattern of reactivity in the peripheral airways of the sheep lung. The size of the panel facilitated a comprehensive description of the glycoconjugate localization on the airway epithelium. Four lectins (agglutinins for Helix aspersa, Psophocarpus tetragonolobus, Trichosanthes kirilowii, and Griffonia simplifolia II) revealed selective reactivity with the small airway epithelium. On lectin Western blotting, these four lectins demonstrated a common low molecular weight banding profile that was distinct from control lectins. The histochemical staining patterns and Western blotting profiles provided evidence for the selective expression of membrane glycoconjugates in the peripheral airways of the sheep lung.