Effects of six different cytokines on lymphocyte adherence to microvascular endothelium and in vivo lymphocyte migration in the rat

The first step in the migration of lymphocytes out of the blood is adherence of lymphocytes to endothelial cells (EC) in the postcapillary venule. It is thought that in inflammatory reactions cytokines activate the endothelium to promote lymphocyte adherence and migration into the inflammatory site. Injection of IFN-gamma, IFN-alpha/beta, and TNF-alpha into the skin of rats stimulated the migration of small peritoneal exudate lymphocytes (sPEL) into the injection site, and these cytokines mediated lymphocyte recruitment to delayed-type hypersensitivity, sites of virus injection, and in part to LPS. The effect of cytokines on lymphocyte adherence to rat microvascular EC was examined. IFN-gamma, IFN-alpha/beta, IL-1, TNF-alpha, and TNF-beta increased the binding of small peritoneal exudate lymphocyte (sPEL) to EC. IFN-gamma was more effective and stimulated adherence at much lower concentrations than the other cytokines. IL-2 did not increase lymphocyte adherence. LPS strongly stimulated lymphocyte binding. Treatment of EC, but not sPEL, enhanced adhesion, and 24 h of treatment with IFN-gamma and IL-1 induced near maximal adhesion. Lymph node lymphocytes, which migrate poorly to inflammatory sites, adhered poorly to unstimulated and stimulated EC, whereas sPEL demonstrated significant spontaneous adhesion which was markedly increased by IFN-gamma, IL-1, and LPS. Spleen lymphocytes showed an intermediate pattern of adherence. Combinations of IFN-gamma and TNF-alpha were additive in stimulating sPEL-EC adhesion. Depletion of sPEL and spleen T cells by adherence to IFN-gamma stimulated EC decreased the in vivo migration of the lymphocytes to skin sites injected with IFN-gamma, IFN-alpha/beta, TNF-alpha, poly I:C, LPS, and to delayed-type hypersensitivity reactions by 50%, and significantly increased the migration of these cells to normal lymph nodes, as compared to unfractionated lymphocytes. Thus the cytokines and lymphocytes involved in migration to cutaneous inflammation in the rat stimulate lymphocyte adhesion to rat EC in vitro, and IFN-gamma stimulated EC appear to promote the selective adhesion of inflammatory site-seeking lymphocytes.     

The influence of strong transplantation antigens (Ag-B) on lymphocyte migration in vivo.

The tissue localization of syngeneic thoracic duct lymphocytes was compared to that of allogeneic cells in four rat strain combinations differing at the Ag-B locus (HO → DA, DA → HO, AO → HO, HO → AO). Dual isotope labeling with [³H]uridine and [¹⁴C]uridine was applied in order so that the distribution of allogeneic and syngeneic cells could be followed in one recipient. During the first couple of hours after iv injection, allogeneic lymphocytes usually migrated as easily into the various tissues as did syngeneic cells. However, after 24 and 48 hr, a reduced amount of label associated with allogeneic cells was often measured in the tissues. This reduction differed in magnitude in the different strain combinations and was most pronounced in the lymph nodes. A reduced number of allogeneic cells also appeared in the thoracic duct. By contrast, no reduced localization of allogeneic lymphocytes was measured in the draining popliteal lymph nodes late after sc injection. In preimmunized animals allogeneic cells were rapidly removed from the blood and therefore failed to localize in the lymphoid tissues. Furthermore, the lymph node localization of allogeneic cells was more like that of syngeneic cells in splenectomized rats, as well as in irradiated recipients (when the irradiation was given shortly before cell transfer). It is concluded that transplantation antigens play no essential role in the interaction between recirculating lymphocytes and the venous endothelium at the sites where the large-scale physiological emigration of the cells takes place (the HEVS of the lymph nodes and the marginal zone vessels of the spleen). The elimination of allogeneic cells is found later; it probably takes place in the lymph nodes and spleen. Possible mechanisms responsible for this rapid removal of allogeneic lymphocytes in nonimmunized recipients are discussed.     

Siderophore typing,a powerful tool for the identification of fluorescent and nonfluorescent pseudomonads

A total of 301 strains of fluorescent pseudomonads previously characterized by conventional phenotypic and/or genomic taxonomic methods were analyzed through siderotyping, i.e., by the isoelectrophoretic characterization of their main siderophores and pyoverdines and determination of the pyoverdine-mediated iron uptake specificity of the strains. As a general rule, strains within a well-circumscribed taxonomic group, namely the species Pseudomonas brassicacearum, Pseudomonas fuscovaginae, Pseudomonas jessenii, Pseudomonas mandelii, Pseudomonas monteilii, "Pseudomonas mosselii," "Pseudomonas palleronii," Pseudomonas rhodesiae, "Pseudomonas salomonii," Pseudomonas syringae, Pseudomonas thivervalensis, Pseudomonas tolaasii, and Pseudomonas veronii and the genomospecies FP1, FP2, and FP3 produced an identical pyoverdine which, in addition, was characteristic of the group, since it was structurally different from the pyoverdines produced by the other groups. In contrast, 28 strains belonging to the notoriously heterogeneous Pseudomonas fluorescens species were characterized by great heterogeneity at the pyoverdine level. The study of 23 partially characterized phenotypic clusters demonstrated that siderotyping is very useful in suggesting correlations between clusters and well-defined species and in detecting misclassified individual strains, as verified by DNA-DNA hybridization. The usefulness of siderotyping as a determinative tool was extended to the nonfluorescent species Pseudomonas corrugata, Pseudomonas frederiksbergensis, Pseudomonas graminis, and Pseudomonas plecoglossicida, which were seen to have an identical species-specific siderophore system and thus were easily differentiated from one another. Thus, the fast, accurate, and easy-to-perform siderotyping method compares favorably with the usual phenotypic and genomic methods presently necessary for accurate identification of pseudomonads at the species level.     

Effects of interleukin-8 on suppression of human lymphocyte polarization and migration by anti-LFA-1 antibody.

We investigated the role of lymphocyte function-associated antigen 1 (LFA-1) in human T cell polarization and migration assay by using monoclonal antibody specific to beta chain (CD18) and alpha chain (CD11a). T cell polarization in response to fetal calf serum (FCS) and colchicine was suppressed by the addition of CD18 and CD11a antibodies. Furthermore, T cell migration in response to lymphocyte chemotactic factor (LCF) and casein was markedly depressed by the addition of CD18 and CD11a antibodies. Additional studies to evaluate effects of interleukin 8 (IL-8) on polarization and migration of T cells preincubated with CD18 or CD11a antibody showed that IL-8 restored the capability of migration of T cells, whereas did not restore polarization activity of such cells. These studies indicate that LFA-1 plays a role in the polarization and migration of T cells and that IL-8 may positively interfer with LFA-1-adhesion molecules.     

Targeting and tracing antigens in live cells with fluorescent nanobodies

We fused the epitope-recognizing fragment of heavy-chain antibodies from Camelidae sp. with fluorescent proteins to generate fluorescent, antigen-binding nanobodies (chromobodies) that can be expressed in living cells. We demonstrate that chromobodies can recognize and trace antigens in different subcellular compartments throughout S phase and mitosis. Chromobodies should enable new functional studies, as potentially any antigenic structure can be targeted and traced in living cells in this fashion.     

Monitoring lymphocyte proliferation in vitro and in vivo with the intracellular fluorescent dye carboxyfluorescein diacetate succinimidyl ester

This protocol outlines the carboxyfluorescein diacetate succinimidyl ester (CFSE) method for following the proliferation of human lymphocytes in vitro and mouse lymphocytes both in vitro and in vivo. The method relies on the ability of CFSE to covalently label long-lived intracellular molecules with the highly fluorescent dye, carboxyfluorescein. Following each cell division, the equal distribution of these fluorescent molecules to progeny cells results in a halving of the fluorescence of daughter cells. The CFSE labeling protocol described, which typically takes <1 h to perform, allows the detection of up to eight cell divisions before CFSE fluorescence is decreased to the background fluorescence of unlabeled cells. Protocols are outlined for labeling large and small numbers of human and mouse lymphocytes, labeling conditions being identified that minimize CFSE toxicity but maximize the number of cell divisions detected. An important feature of the technique is that division-dependent changes in the expression of cell-surface markers and intracellular proteins are easily quantified by flow cytometry.     

T and B lymphocyte migration into syngeneic tumors.

The migration of splenic T and B lymphocytes into syngeneic tumors undergoing immunologic rejection was investigates. Spleen cells were obtained from normal BALC/c mice or BALB/c mice bearing tumors induced by murine sarcoma virus (MSV). Either whole spleen cells or immunoabsorbent purified T and B cells were radiolabeled with sodium chromate-51 and injected i.v. into normal or MSV inducted-tumor bearing syngeneic recipients. Twenty-four hours later the recipient mice were sacrificed and radioactivity was assessed for tumor, contralateral normal muscle, the lymph nodes draining the tumor and contralateral draining lymph nodes, peripheral lymph nodes, spleen, and liver. Both T and B lymphocytes from either normal or MSV tumor-bearing animals show greatly increased migration into the tumor when compared with normal muscle. Migration of T cells from both normal and MSV tumor bearers was 30 times that of migration to normal muscle. B cells from tumor-bearing mice, on the other hand, localized in the tumor itself only 50% as frequently as did B cells from normal animals. In addition, T cells from MSV tumor bearers were found in the highest proportion in the lymph node draining the tumor site. We conclude that T and B lymphocytes from either normal or tumor-bearing mice migrate to a syngeneic tumor undergoing immunologic rejection. In contrast, the migration of both T and B cells from tumor-bearing animals was decreased to the peripheral lymph nodes at the time of maximum tumor growth.     

Inhibition of lymphocyte endothelial adhesion and in vivo lymphocyte migration to cutaneous inflammation by TA-3, a new monoclonal antibody to rat LFA-1.

Lymphocyte function-associated Ag-1 (LFA-1) or CD11a/CD18 mediates lymphocyte adhesion to cultured vascular endothelial cells (EC). Thus, LFA-1 likely plays a major role in lymphocyte migration out of the blood, but there is little information on this in vivo. Small peritoneal exudate lymphocytes (sPEL) and lymph node (LN) lymphoblasts adhere to cytokine-activated EC and preferentially migrate to cutaneous inflammatory sites. The role of LFA-1 in the adherence and in vivo migration of these T cells was determined. Because of a lack of anti-rat LFA-1, mAb were prepared to rat T cells. One mAb, TA-3, inhibited homotypic aggregation; T cell proliferation to Ag, alloantigens, and mitogens; stained all leukocytes; and immunoprecipitated 170- and 95-kDa polypeptides from lymphocytes and neutrophils. TA-3 binding to lymphocytes also required Ca2+, but not Mg2+. Thus, TA-3 appears to react with rat LFA-1. TA-3 inhibited spleen T cell adhesion to unstimulated EC by 30% and to IFN-gamma, TNF-alpha, IL-1 alpha, and LPS stimulated EC by 50 to 60% but inhibited sPEL EC adhesion by only 10%. TA-3 also strongly inhibited anti-CD3-stimulated LN T cell adherence. The migration of spleen T cells to delayed-type hypersensitivity and skin sites injected with LPS, poly I:C, IFN-gamma, IFN-alpha/beta, and TNF was inhibited by 72 to 88% by TA-3, and was decreased by 50% to peripheral LN. TA-3 caused less but still 50 to 60% inhibition of sPEL migration to inflamed skin. Lymphoblast migration to skin was inhibited 40 to 80% and to PLN by 30%. Migration of lymphocytes from all sources to mesenteric LN was inhibited by 32 to 60%. In conclusion, LFA-1 mediates much of the adherence of spleen T cells and lymphoblasts to EC in vitro, most of the migration of these cells to dermal inflammation and about 50% of the homing of LN and spleen T cells to peripheral and mesenteric LN. sPEL are less dependent on LFA-1 for adhesion to EC in vitro and for migration to inflamed skin and LN in vivo.     

Lipid rafts in lymphocyte activation and migration

Functional polarization of leukocytes is a requisite to accomplish immune function. Immune synapse formation or chemotaxis requires asymmetric redistribution of membrane receptors, signaling molecules and the actin cytoskeleton. There is increasing evidence that compartmentalization of the plasma membrane into distinct lipid microdomains is pivotal in establishing and maintaining leukocyte polarity. Specific rafts assemble into large-scale domains to create plasma membrane asymmetries at specific cell locations, thus coordinating temporally and spatially cell signaling in these processes. In this review we discuss the roles of lipid rafts as organizers of T lymphocyte polarity during cell activation and migration.     

Haptotactic activity of fibronectin on lymphocyte migration in vitro

In addition to mediating cell adhesion, fibronectin (FN) also affects the migration of different cell types. However, the role of FN in lymphocyte migration is unclear. In this study, we examined the effects of FN on the in vitro migration of lymphocytes. Using the checkerboard analysis in a blind-well microchemotaxis assay, soluble FN was determined to have neither a chemotactic nor chemokinetic effect on spleen or thymus lymphocytes. However, when the nitrocellulose filter was coated unidirectionally with FN, the migration of both spleen and thymus lymphocytes into the filter was enhanced, indicating that FN is haptotactic for lymphocytes. When the filter was coated bidirectionally, no enhancement in migration was observed, indicating that FN is not haptokinetic for lymphocytes. When the FN cell-binding domain and the heparin-binding domain were tested, the cell-binding domain was haptotactic for both spleen and thymus lymphocytes, whereas the heparin-binding domain was only haptotactic for spleen lymphocytes. Because the heparin-binding domain can mediate strong adhesion of thymus lymphocytes, the lack of haptotactic activity is likely to be the result of excessive binding that prevents cell motility.     

Inhibition of in vivo lymphocyte migration to inflammation and homing to lymphoid tissues by the TA-2 monoclonal antibody. A likely role for VLA-4 in vivo.

The adhesion receptors, LFA-1 and VLA-4, on lymphocytes mediate lymphocyte adherence to cytokine-activated endothelial cells (EC) in vitro. Based on our previous data, which suggested that the mAb TA-2 reacted with rat VLA-4, the effect of TA-2 on lymphocyte migration out of the blood was examined. Small peritoneal exudate lymphocytes (sPEL) preferentially migrate to cutaneous inflammatory reactions, whereas lymphocytes from peripheral lymph nodes (PLN) migrate poorly to inflammatory sites but home avidly to PLN. Treatment of sPEL with TA-2 inhibited sPEL migration to DTH, LPS, poly I:C, IFN-gamma, IFN-alpha/beta, and TNF-alpha by 35 to 65% and their accumulation in PLN by 50%. The homing of PLN lymphocytes to PLN was not inhibited by TA-2. Spleen T cell migration to cutaneous inflammatory sites was inhibited but homing to PLN was not affected. Systemic treatment with TA-2 inhibited sPEL migration to inflamed or cytokine-injected skin by up to 70%. Similarly, TA-2 strongly inhibited the migration of Ag-stimulated PLN lymphoblasts to skin and to PLN. The migration of lymphocytes from all sources, including the peritoneum, spleen, PLN, mesenteric nodes, and Peyer's patches, to mesenteric lymph nodes and Peyer's patches was inhibited by 80% and 95%, respectively. In conclusion, our results suggest that VLA-4 and possibly other alpha 4 integrins mediate the migration of the inflammation-seeking sPEL and Ag-activated lymphoblasts to cutaneous inflammatory sites and lymph nodes but do not affect the homing of PLN lymphocytes to PLN. These integrins also appear to be necessary for the migration of all types of lymphocytes to Peyer's patches and mesenteric lymph nodes.     

Chemical methods of DNA and RNA fluorescent labeling.

Several procedures have been described for fluorescent labeling of DNA and RNA. They are based on the introduction of aldehyde groups by partial depurination of DNA or oxidation of the 3'-terminal ribonucleoside in RNA by sodium periodate. Fluorescent labels with an attached hydrazine group are efficiently coupled with the aldehyde groups and the hydrazone bonds are stabilized by reduction with sodium cyanoborohydride. Alternatively, DNA can be quantitatively split at the depurinated sites with ethylenediamine. The aldimine bond between the aldehyde group in depurinated DNA or oxidized RNA and ethylenediamine is stabilized by reduction with sodium cyanoborohydride and the primary amine group introduced at these sites is used for attachment of isothiocyanate or succinimide derivatives of fluorescent dyes. The fluorescent DNA labeling can be carried out either in solution or on a reverse phase column. These procedures provide simple, inexpensive methods of multiple DNA labeling and of introducing one fluorescent dye molecule per RNA, as well as quantitative DNA fragmentation and incorporation of one label per fragment. These methods of fluorophore attachment were shown to be efficient for use in the hybridization of labeled RNA, DNA and DNA fragments with oligonucleotide microchips.     

Neural projections in planarian brain revealed by fluorescent dye tracing

The planarian brain has an inverted-U shaped structure with functional regionalization. To investigate how each region in the brain connects to each other, we traced neural projections by microinjection of fluorescence dye tracers. We found that external light and olfactory/taste signals received in the head region are conveyed in the main lobes (sponge region) of the brain. Chemosensory neurons distributed in the lateral branches project to the peripheral region of the sponge and visual neurons project to the medial region of the sponge. Parts of the sensory neurons project directly to the corresponding sensory neurons on the opposite side of the brain. However, all of the dye labeled brain neurons in the left and right lobes connect to each other via commissural neurons in the central region of the sponge. In addition to these observations, we detected regional differences in the planarian visual neurons. Posterior visual neurons have ipsilateral projection, but anterior visual neurons project to the contralateral side of the brain. A pair of longitudinal ventral nerve cords (VNC) connect to the brain on the ventral side, suggesting that they transmit signals which are integrated and processed in the brain. We also detected the direct connection of neurons in the brain and those of the pharynx, even though most pharynx neurons connect to VNC neurons. Here, we report for the first time on neural connections in the planarian central nervous system after overcoming technical difficulties specific to flatworms.     

Vimentin function in lymphocyte adhesion and transcellular migration

Although the adhesive interactions of leukocytes with endothelial cells are well understood, little is known about the detailed mechanisms underlying the actual migration of leukocytes across the endothelium (diapedesis). Leukocytes have been shown to use both paracellular and transcellular routes for transendothelial migration. Here we show that peripheral blood mononuclear cells (PBMCs; T- and B-lymphocytes) preferentially use the transcellular route. The intermediate filaments of both endothelial cells and lymphocytes formed a highly dynamic anchoring structure at the site of contact between these two cell types. The initiation of this process was markedly reduced in vimentin-deficient (vim(-/-)) PBMCs and endothelial cells. When compared with wild-type PBMCs, vim(-/-) PBMCs showed a markedly reduced capacity to home to mesenteric lymph nodes and spleen. Furthermore, endothelial integrity was compromised in vim(-/-) mice, demonstrating that intermediate filaments also regulate the barrier that governs leukocyte extravasation. Absence of vimentin resulted in highly aberrant expression and distribution of surface molecules critical for homing (ICAM-1 and VCAM-1 on endothelial cells and integrin-beta1 on PBMCs). These data show that intermediate filaments are active in lymphocyte adhesion and transmigration.     

Characterization of fluorescent and nonfluorescent peptide siderophores produced by Pseudomonas syringae strains and their potential use in strain identification

Nonfluorescent highly virulent strains of Pseudomonas syringae pv. aptata isolated in different European countries and in Uruguay produce a nonfluorescent peptide siderophore, the production of which is iron repressed and specific to these strains. The amino acid composition of this siderophore is identical to that of the dominant fluorescent peptide siderophore produced by fluorescent P. syringae strains, and the molecular masses of the respective Fe(III) chelates are 1,177 and 1,175 atomic mass units. The unchelated nonfluorescent siderophore is converted into the fluorescent siderophore at pH 10, and colors and spectral characteristics of the unchelated siderophores and of the Fe(III)-chelates in acidic conditions are similar to those of dihydropyoverdins and pyoverdins, respectively. The nonfluorescent siderophore is used by fluorescent and nonfluorescent P. syringae strains. These results and additional mass spectrometry data strongly suggest the presence of a pyoverdin chromophore in the fluorescent siderophore and a dihydropyoverdin chromophore in the nonfluorescent siderophore, which are both ligated to a succinamide residue. When chelated, the siderophores behave differently from typical pyoverdins and dihydropyoverdins in neutral and alkaline conditions, apparently because of the ionization occurring around pH 4.5 of carboxylic acids present in beta-hydroxyaspartic acid residues of the peptide chains. These differences can be detected visually by pH-dependent changes of the chelate colors and spectrophotochemically. These characteristics and the electrophoretic behavior of the unchelated and chelated siderophores offer new tools to discriminate between saprophytic fluorescent Pseudomonas species and fluorescent P. syringae and P. viridiflava strains and to distinguish between the two siderovars in P. syringae pv. aptata.     

Basement membrane and its components on lymphocyte adhesion, migration, and proliferation.

During inflammation and recirculation, lymphocytes migrate into tissues by traversing the capillary endothelium, a process known as extravasation. After crossing the endothelial cells, lymphocytes come into contact with the basement membrane, which is a specialized layer of extracellular matrix containing predominantly laminin, collagen type IV, entactin, and heparan sulfate proteoglycans. In tissue invasion by inflammatory cells and metastatic tumor cells, the basement membrane serves as a substratum for cell adhesion and migration. However, the role of basement membrane in lymphocyte extravasation remains unclear. In this study, we investigated the effect of basement membrane on lymphocyte adhesion, migration, and proliferation, using matrigel as a model for basement membrane. We observed that matrigel promotes both lymphocyte adhesion and migration, with entactin primarily responsible for promoting adhesion and laminin for promoting migration. In addition, activation of lymphocytes by anti-CD3 enhances their adhesion and migration on matrigel-coated substratum. We also observed that matrigel inhibits the proliferation of lymphocytes stimulated by Con A. Furthermore, we demonstrated that laminin is the matrigel component responsible for inhibiting lymphocyte proliferation. However, matrigel has no effect on the proliferation of lymphocytes stimulated by LPS. These results suggest that matrigel has different effects on lymphocyte subpopulations. In agreement with the results on proliferation, matrigel also inhibits the production of IL-2 by Con A-stimulated lymphocytes.     

Human lymphocyte migration in vitro: characterization and quantitation of locomotory parameters.

Using a time-lapse cinephotomicrographic technique, the locomotory paths taken by lymphocytes have been shown to satisfy the requirements for a continuous-time Markov chain analysis consisting of four directional states defined by the four quadrants of a Cartesian plane and state 0 in which the cells are stationary. The important parameters characterizing this path motion are the average time (waiting time) that a cell spends in each state and the state transition probabilites which, using the Markov model, allow the computation of the probability of the cells moving in a given direction. Our results show that lymphocytes moving alone on glass exhibit a random migration pattern.     

Dendritic cell migration and lymphocyte homing imprinting

For an effective adaptive immune response to occur, dendritic cells (DC), which are the most efficient antigen-presenting cells, must be able to sample the peripheral microenvironment and migrate towards secondary lymphoid organs (SLO) where they activate naive lymphocytes. Upon activation, lymphocytes proliferate and acquire the capacity to migrate to extralymphoid compartments. Although the molecular mechanisms controlling lymphocyte homing to lymphoid and to some extralymphoid tissues have been described in significant detail, it is much less clear how DC migration is controlled. Do DC obey similar adhesion cues that lymphocytes do, or do they have their own "zip codes"? This is relevant from a therapeutic standpoint because effective DC-based vaccines should be able to reach the appropriate tissues in order to generate protective immune responses. Here, we discuss some of the mechanisms used by DC to reach their target tissues. Once DC arrive at their destination, they are exposed to the tissue microenvironment, which likely modulates their functional properties in a tissue-specific fashion. This local DC "education" is probably responsible among other things; for the acquisition of tissue-specific homing imprinting capacity by which DC instruct lymphocytes to migrate to specific tissues. Finally, we discuss how dysregulation of these signals may play a key role in disease.