The regulation of lymphocyte traffic

Physiologically Based Pharmacokinetic Modeling of 3 HIV Drugs in Combination and the Role of Lymphatic System after Subcutaneous Dosing. Part 2: Model for the Drug-combination Nanoparticles

We previously developed a mechanism-based pharmacokinetic (MBPK) model to characterize the PK of a lymphocyte-targeted, long-acting 3 HIV drug-combination nanoparticle (DcNP) formulation of lopinavir, ritonavir, and tenofovir. MBPK describes time-courses of plasma drug concentration and has provided an initial hypothesis for the lymphatic PK of DcNP. Because anatomical and physiological interpretation of MBPK is limited, in this Part 2, we report the development of a Physiologically Based Pharmacokinetic (PBPK) model for a detailed evaluation of the systemic and lymphatic PK of drugs associated with DcNP. The DcNP model is linked to the PBPK model presented earlier in Part 1 to account for the disposition of released free drugs. A key feature of the DcNP model is the uptake of the injected dose from the subcutaneous site to the adjacent lymphoid depot, routing through the nodes within and throughout the lymphatic network, and its subsequent passage into the blood circulation. Furthermore, the model accounts for DcNP transport to the lymph by lymphatic recirculation and mononuclear cell migration. The present PBPK model can be extended to other nano-drug combinations that target or transit through the lymphatic system. The PBPK model may allow scaling and prediction of DcNP PK in humans.

Imprinting of Skin/Inflammation Homing in CD4+ T Cells Is Controlled by DNA Methylation within the Fucosyltransferase 7 Gene

E- and P-selectin ligands (E- and P-ligs) guide effector memory T cells into skin and inflamed regions, mediate the inflammatory recruitment of leukocytes, and contribute to the localization of hematopoietic precursor cells. A better understanding of their molecular regulation is therefore of significant interest with regard to therapeutic approaches targeting these pathways. In this study, we examined the transcriptional regulation of fucosyltransferase 7 (FUT7), an enzyme crucial for generation of the glycosylated E- and P-ligs. We found that high expression of the coding gene fut7 in murine CD4⁺ T cells correlates with DNA demethylation within a minimal promoter in skin/inflammation-seeking effector memory T cells. Retinoic acid, a known inducer of the gut-homing phenotype, abrogated the activation-induced demethylation of this region, which contains a cAMP responsive element. Methylation of the promoter or mutation of the cAMP responsive element abolished promoter activity and the binding of CREB, confirming the importance of this region and of its demethylation for fut7 transcription in T cells. Furthermore, studies on human CD4⁺ effector memory T cells confirmed demethylation within FUT7 corresponding to high FUT7 expression. Monocytes showed an even more extensive demethylation of the FUT7 gene whereas hepatocytes, which lack selectin ligand expression, exhibited extensive methylation. In conclusion, we show that DNA demethylation within the fut7 gene controls selectin ligand expression in mice and humans, including the inducible topographic commitment of T cells for skin and inflamed sites.

Most B cells in non-lymphoid tissues are naïve

The current view of lymphocyte migration states that naïve lymphocytes re-circulate between the blood and the lymph via the lymph nodes, but are not able to access non-lymphoid tissues. We examined B lymphocytes in peripheral tissues and found that the majority were phenotypically similar to naïve B cells in lymphoid tissues and were located within the parenchyma, not associated with blood vessels. The mutation rate within the Vh region of these cells was substantially less than the rate attributed to somatic hypermutation and was identical to that observed in naïve B cells isolated from the lymph nodes, showing the presence of naïve B cells in the non-lymphoid organs. Further, using FTY720-treated mice, we showed that naïve B cells migrate through the peripheral tissues and, using pertussis toxin, that the entry of B cells was not controlled by chemokine-mediated signalling events. Overall, these results show that naïve B lymphocytes constitute the majority of the total B-cell population in non-lymphoid tissues and suggest that these cells may re-circulate through the periphery as part of their normal migration pathway. This has implications for the current view of the role of naïve B cells in priming and tolerance.

Cellular changes in hepatocytes and intestinal endothelium after hepatoduodenal ligament occlusion and protective effects of caspase inhibition

INTRODUCTION

Hepatic vascular control is used by many surgeons to prevent massive hemorrhage during hepatectomy. However, this may carry a risk of ischemic damage to the hepatocytes. Another major drawback of intraoperative occlusion of the hepatoduodenal ligament is portal stasis with resultant intestinal congestion which may cause adverse effects on the intestinal functions. CD44 is a transmembrane glycoprotein present in many types of epithelial cells. By mediating the attachment of dividing crypt cells to the basal lamina via hyaluronan, CD44 is considered to play a role in maintaining the intestinal villus integrity. Apoptosis is a pathway of cell death orchestrated by a family of proteases called caspases. ZVAD-fmk is a cell-permeable irreversible inhibitor of caspase and might block the processing of many caspases. This study is designed with the purpose to evaluate the impact of intraoperative occlusion of the hepatoduodenal ligament on hepatocyte and intestine functions and also to evaluate the potential influence of ZVAD-fmk on the hepatocyte and intestine functions.

MATERIALS AND METHODS

Male Sprague-Dawley rats were randomized to 5 groups. Group 1(C) underwent sham operation. Group 2 (HDL30) underwent occluding the hepatoduodenal ligament by for 30 minutes. Group 3 (HDL 15) underwent occluding the hepatoduodenal ligament by for 15 minutes, releasing for 5 minutes, underwent occlusion for another 15 minutes. Group 4 (ZHDL30) first received ZVAD-fmk, then underwent occluding the hepatoduodenal ligament by for 30 minutes. Group 5 (ZHDL15) first received ZVAD-fmk, then underwent occluding the hepatoduodenal ligament for 15 minutes, releasing for 5 minutes, underwent occlusion for another 15 minutes. After removing the temporary occlusion, liver tissue and proximal jejunum were harvested. Hepatocyte and intestine apoptosis were quantitated using the TUNEL method. CD 44 status of jejunum were determined by immunohistochemical staining.

RESULTS

Hepatocyte apoptosis was significantly increased in group (HDL30) and group (HDL15) when compared with group (C). ZVAD-fmk effectively attenuated this phenomenon in both groups. There was no significant difference between group (HDL30) and group (HDL15). Jejunal apoptosis was significantly increased in group (HDL30) and group (HDL15) when compared with group (C). ZVAD-fmk effectively attenuated this phenomenon in both groups. There was no significant difference between group (HDL30) and group (HDL15). CD44 expression on jejunum was significantly increased in group (HDL30) and group (HDL15) when compared with group (C). ZVAD-fmk failed to effectively diminish this phenomenon.

CONCLUSION

Occlusion of the hepatoduodenal ligament significantly increased both hepatocyte and jejunal apoptosis and pretreatment with ZVAD-fmk could effectively diminish such phenomenon. CD44 expression on jejunum was also significantly increased by intraoperative occlusion of the hepatoduodenal ligament, yet pretreatment with ZVAD-fmk failed to show significant effect on such phenomenon.

Oropharyngeal administration of colostrum to extremely low birth weight infants: theoretical perspectives

Studies in adults have shown that the oropharyngeal route can be used to effectively and safely administer interferon-alpha, an immune cell-derived cytokine, to patients who are unable to tolerate its parenteral administration. The mechanism for this appears to be the stimulatory effects of the cytokine, on the oropharyngeal-associated lymphoid tissue system. Own mother's colostrum (OMC) is rich in cytokines and other immune agents that provide bacteriostatic, bacteriocidal, antiviral, anti-inflammatory and immunomodulatory protection against infection. OMC may be especially protective for the extremely low birth weight (ELBW) infant in the first days of life; however clinical instability typically precludes enteral feedings during this period. Oropharyngeal administration is a potential alternative method of providing OMC. Oropharyngeal administration of OMC may have immunomodulatory effects on the recipient infant, and would be especially beneficial to the ELBW infant who would otherwise remain nil per os during the first days of life.

Environmental cues, dendritic cells and the programming of tissue-selective lymphocyte trafficking

Lymphocytes are imprinted during activation with trafficking programs (combinations of adhesion and chemoattractant receptors) that target their migration to specific tissues and microenvironments. Cytokines contribute, but, for gut and skin, evolution has cleverly adapted external cues from food (vitamin A) and sunlight (ultraviolet-induced vitamin D3) to imprint lymphocyte homing to the small intestines and T cell migration into the epidermis. Dendritic cells are essential: they process the vitamins to their active metabolites (retinoic acid and 1,25(OH)(2)D3) for presentation with antigen to lymphocytes, and they help export environmental cues through lymphatics to draining lymph nodes, to program the trafficking and effector functions of naive T and B cells.

Evidence that a significant number of naive T cells enter non-lymphoid organs as part of a normal migratory pathway

Only activated and effector memory T cells are thought to access non-lymphoid tissues. In contrast, naive T cells are thought to circulate only between the blood, lymph and secondary lymphoid organs. We examined the phenotype of endogenous T cells in various non-lymphoid organs and showed that a subset of cells exhibited an apparently naive phenotype and were functionally inactive. FTY720 treatment selectively depleted this population from the non-lymphoid tissues. In addition, RAG-deficient TCR transgenic CD4 and CD8 T cells were present in non-lymphoid tissues in bone marrow chimeric mice and in situ imaging analysis revealed their location in the parenchymal tissues. Moreover, migration of TCR transgenic T cells to non-lymphoid tissues after adoptive transfer was pertussis-toxin resistant. Overall, the results suggest that naive T cells may circulate through non-lymphoid tissues as part of their normal migratory pathway.

L-selectin: adhesion, signalling and its importance in pathologic posttraumatic endotoxemia and non-septic inflammation

The leucocyte expressed surface-bound L-selectin belongs to the selectin family of adhesion molecules. It exhibits adhesive as well as signalling functions. Mainly, it is of importance in lymphocyte homing and in the extravasation of leucocytes into the surrounding tissue during inflammation. Acting in the initial step of the cell adhesion cascade, L-selectin is responsible for the rolling of leucocytes on endothelial layers. Therefore, L-selectin is thought to be an adequate target for pharmacological interventions. Beneath the discussion of the molecules' general features like molecule structure and its regulation, the review focuses firstly on L-selectin in the context of posttraumatic inflammatory disorders, and secondly on the importance of L-selectin specific signalling events.

T cell traffic signals

In 1990, Charles Mackay and colleagues combined classical physiology with modern molecular biology to provide the first concrete evidence that naive and memory T cells follow distinct migratory routes out of the bloodstream— a discovery that helped invigorate the field of lymphocyte homing.

CD11b-mediated migratory property of peripheral blood B cells

BACKGROUND

CD11b belongs to the integrin family and is expressed on neutrophils, monocytes, natural killer cells, and a subset of lymphocytes. Although CD11b expressed on neutrophils and monocytes has been extensively investigated and has been reported to play an important role in the migration of these subsets of leukocytes, the function of CD11b expressed on a subset of B cells has not yet been clarified.

OBJECTIVE

To elucidate the functional activity of CD11b expressed on B cells, we characterized the CD11b-expressing cells among the B-cell population and investigated their migratory ability.

METHODS

Isolated peripheral blood CD19 + B cells were analyzed by flow cytometry. The migratory ability of B cells was evaluated by the transwell assay, and the contribution of CD11b to this ability was investigated by using an anti-CD11b blocking mAb.

RESULTS

The majority of CD27 - IgD + naive B cells were CD11b - , whereas most CD27 + memory cells were CD11b +. Among the CD27 + memory cells, expression of CD11b was stronger on the IgD - cells than on the IgD + cells. In the transwell assay, the migrating cells were predominantly CD27 + IgD - cells, most of which expressed CD11b. The addition of an anti-CD11b blocking mAb resulted in the significant reduction of the number of migrating B cells.

CONCLUSION

Memory B cells express CD11b and, in contrast with naive B cells, have high migratory ability. CD11b plays an essential role in the homing process of memory cells.

Effects of implantation and early pregnancy on the expression of cytokines and vascular surface molecules in the sheep endometrium

Successful implantation is a highly coordinated process involving changes in cytokines, adhesion molecules, hormones, enzymes and growth factors. This study examines the expression of key cytokines and vascular surface molecules in the pregnant uterus of sheep around the time of implantation. Uterine tissues and uterine washings were collected from non-pregnant and pregnant sheep at 17-19 days post-coitus (dpc), 26-27 and 34-36 dpc. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of caruncular/placentomal tissues revealed that cytokines IL-2, IL-4 and IL-8, which were not detected in non-pregnant uterus, were induced more strongly at 26-27 dpc than at other stages of pregnancy tested. Cytokines LIF, IL-6, IL-10, TNF-alpha were also most highly expressed at 26-27 dpc, expression of them being lower at other time-points during early pregnancy and non-pregnancy. The cytokines IL-1beta, IFN-gamma and TGF-beta were expressed in all non-pregnant and pregnant tissues examined. Enzyme-linked immunosorbent assay (ELISA) performed on uterine washings clearly detected the presence of IL-1alpha protein at 26-27 and 34-36 dpc. Immunohistochemistry revealed that expression of vascular adhesion molecule VCAM-1 in endometrial endothelium was strongly induced at 26-27 dpc in the pregnant endometrium. Expression of CD5 on vascular endothelium was not induced in placentomal tissues until 26-27 dpc and was further increased by 34-36 dpc. These results demonstrate a dynamic change in a wide range of cytokines during early stages of pregnancy, with a critical period around 26-27 dpc. In addition, at 26-27 dpc, expression of the surface/adhesion molecules, CD5 and VCAM-1, is induced on vascular endothelium of the sheep endometrium, possibly as a direct consequence of the changed cytokine environment, and may be involved in directing the changes in leucocyte migration observed during pregnancy.

CD44, alpha(4) integrin, and fucoidin receptor-mediated phagocytosis of apoptotic leukocytes

Various types of phagocytes mediate the clearance of apoptotic cells. We previously reported that human and murine high endothelial venule (HEV) cells ingest apoptotic cells. In this report, we examined endothelial cell fucoidin receptor-mediated phagocytosis using a murine endothelial cell model mHEV. mHEV cell recognition of apoptotic leukocytes was blocked by fucoidin but not by other phagocytic receptor inhibitors such as mannose, fucose, N-acetylglucosamine, phosphatidylserine (PS), or blocking anti-PS receptor antibodies. Thus, the mHEV cells used fucoidin receptors for recognition and phagocytosis of apoptotic leukocytes. The fucoidin receptor-mediated endothelial cell phagocytosis was specific for apoptotic leukocytes, as necrotic cells were not ingested. This is in contrast to macrophages, which ingest apoptotic and necrotic cells. Endothelial cell phagocytosis of apoptotic cells did not alter viable lymphocyte migration across these endothelial cells. Antibody blocking of CD44 and alpha4 integrin on the apoptotic leukocyte inhibited this endothelial cell phagocytosis, suggesting a novel function for these adhesion molecules in the removal of apoptotic targets. The removal of apoptotic leukocytes by endothelial cells may protect the microvasculature, thus ensuring that viable lymphocytes can successfully migrate into tissues.

Entrapment of recent thymic emigrants in lymphoid tissues from HIV-infected patients: association with HIV cellular viral load

OBJECTIVE(S)

Depletion of thymus derived naive T-cells is a feature of HIV infection. Here the impact of HIV infection on the compartmentalization of recent thymic emigrants of (RTE) and naive T-cells was examined.

METHODS

Peripheral blood mononuclear cells (PBMC) and lymphoid tissue (LT) from 43 HIV-infected patients and 12 controls were examined for RTE distribution by measuring coding joint T-cell receptor excisional circles (cjTREC) by PCR and naive and memory T-cell subsets and adhesion molecules (L-selection, LFA-1) by flow cytometry.

RESULTS

In HIV-infected patients, the RTE as quantified by cjTRECs in CD4 LT cells were significantly higher than in PBMC. Their values, however, were less than in control subjects, in both the LT and PBMC compartments. This was associated with an increase in L-selectin and LFA-1 expression on LT derived T cells. In PBMC, a significant positive relationship between TREC and naive CD4 cells and an inverse relationship between TREC and cellular viral load (CVL) was observed. Whereas in LT, there was a positive relationship between cjTREC and both naive CD4 cell percentage and CVL.

CONCLUSIONS

Collectively, the data suggests that LT is a significant reservoir for RTE. The RTE appeared to be entrapped in LT from HIV-infected subjects. Such entrapment is probably a response to the high viral load in these tissues. These observations may partially explain the decline in RTE observed in the peripheral blood of HIV-infected patients, and the delay in recovery of naive cells in blood after initiation of HAART.

Distribution of adoptively transferred, tumor-sensitized lymphocytes in the glioma-bearing rat

For adoptively transferred lymphocytes to exert anti-tumor effects in vivo, they must traffic or initiate the migration of endogenous immune cells to the site of tumor. Using a rat model, we examined the trafficking of tumor-sensitized lymphocytes to an intracerebral glioma. By labeling the cells with 111Indium oxine (111In) prior to intravenous injection, we were able to quantify the relative number of lymphocytes that traveled to the tumor site. There was no difference in lymphocytic influx between the tumor-bearing and non-tumor-bearing cerebral hemispheres in 3-day rat glioma models. However, in 7-day models, significantly greater numbers of 111In-labeled lymphocytes resided in the tumor-bearing hemisphere at 12 h post-administration. This number increased more than two-fold by 24 h post-adoptive transfer. Using fluorescent-labeled lymphocytes and microscopy, we confirmed that the detection of radioactivity within the brain was truly due to tumor infiltrating 111In-labeled lymphocytes. Adoptively transferred cells were found in perivascular and peritumoral locations. These data demonstrate that tumor-sensitized lymphocytes traffic to an intracerebral target site where they can exert an effect, further supporting adoptive immunotherapy as a treatment for glioma.

Induction and characterization of cutaneous lymphocyte antigen on natural killer cells

Cutaneous lymphocyte antigen (CLA) has been reported to be expressed mainly by memory/effector T lymphocytes infiltrating inflammatory skin lesions and cutaneous T-cell lymphoma. It has been suggested that CLA is a specific homing receptor, facilitating the T-cell migration into skin lesions, and also an indicator of the skin-homing T-cell subset. In the present study, we investigated the expression of CLA in natural killer (NK) cells defined phenotypically as surface CD3- and CD56+ cells in peripheral blood. CLA was definitely expressed on CD3-CD56+ cells at a level comparable to CD3+ cells in peripheral blood of normal Japanese volunteers. After in vitro stimulation of peripheral blood mononuclear cells with interleukin 2 (IL-2) and IL-12, there was a significant increase in the number and percentage of CLA+ NK cells but not CLA+ T cells (P < 0.01). To analyse the characteristics of CLA expressed by NK cells, we investigated a CLA+ NK-leukaemia cell line, NK-YS, established from a patient with NK leukaemia/lymphoma with skin infiltration. In the in vitro study, the CLA-expressing NK-leukaemic cell line bound to E-selectin-transfected cells and was inhibited by HECA 452 antibody or neuraminidase treatment of leukaemic cells. These findings suggest that CLA expressed by NK cells is a homing receptor for the E-selectin molecule and may explain skin infiltration by NK cells and NK lymphoma cells analogous to T cells. An NK-cell subset expressing CLA must play an important role in host defence against microorganisms and neoplasms in skin lesions.

Pharmacokinetics and cell trafficking dynamics of 2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol hydrochloride (FTY720) in cynomolgus monkeys after single oral and intravenous doses

The pharmacokinetics and cell trafficking dynamics of 2-amino-2-[2-(4-octylphenyl)ethyl]propane-1,3-diol hydrochloride (FTY720), a novel immunosuppressive agent, were examined in cynomolgus monkeys (three males and three females). After single doses of 0.1 mg/kg p.o. or i.v. bolus and 1 mg/kg p.o. were administered to the animals, the concentrations of FTY720, and the numbers of lymphocytes, CD20+CD2-B cells, and CD2+CD20-T cells in blood were measured over 23 days. A linear three-compartment model characterized the time course of FTY720 concentrations with a terminal half-life of about 31 h, clearance of about 0.53 l/h/kg, and bioavailability of about 38%. The dynamic responses were not area under the curve (or dose) proportional for either males or females. An indirect response model with a distribution pool captured the cell trafficking data for all doses for each cell type, where initial blood counts (R(0)) were about 7650, 2100, and 5250 cells/microl; maximum fractional inhibition (I(max)) about 0.88, 0.85, and 0.91; influx (k(in)) about 6014, 1312, and 5662 cells/microl/h; efflux (k(out)) about 0.798, 0.555, and 1.08 h(-1); intercompartmental k(cp) about 0.134, 0.192, and 0.082 h(-1); and intercompartmental k(pc) rate constants about 3.9 x 10(-4), and 0.016 and 8.9 x 10(-6) h(-1) for lymphocytes, B cells, and T cells, respectively. The inhibition concentration IC(50) was about 0.48 microg/l for all cells, which was remarkably low. The apparent distribution volumes of peripheral pool (V(p)) were markedly larger than blood volume (V(b)) for all cells. The I(max) for cell trafficking was achieved at doses smaller than that producing graft protection, indicating stronger central than peripheral effects of this drug. The profound cell trafficking effects of FTY720 can be readily captured and interpreted with an extended indirect response model.

Ingested IFN-alpha preserves residual beta cell function in type 1 diabetes

Type 1 diabetes mellitus is a chronic disorder that presumably results from an autoimmune destruction of the insulin-producing pancreatic beta cells. The therapeutic potential of interventions aimed at preventing type 1 diabetes can be assessed in newly diagnosed patients. Because there is a historical experience of a low incidence of spontaneous remission in type 1 diabetes mellitus, interventions preserving beta cell function have been used to identify positive therapeutic outcomes. We treated 10 newly diagnosed type 1 diabetes patients with 30,000 IU ingested interferon-alpha (IFN-alpha) within 1 month of diagnosis and examined the difference between baseline and Sustacal-induced (Mead Johnson Nutritionals, Evansville, IN) C-peptide responses, respectively, at 0, 3, 6, 9, and 12 months. Eight of the ten patients showed preserved beta cell function, with at least a 30% increase in stimulated C-peptide levels at 0, 3, 6, 9, and 12 months after initiation of treatment. There was no discernible chemical or clinical toxicity associated with ingested IFN-alpha. Our results support the potential of ingested IFN-alpha to preserve residual beta cell function in recent onset type 1 diabetes mellitus and the testing of IFN-alpha in a placebo-controlled trial.

Immunity in the mammary gland

The ruminant mammary gland is an extremely important economic organ in that it provides a major nutrition source for a significant portion of the world's human population. The ruminant mammary gland is also responsible for providing protective immunity to neonates and for defending itself from invading pathogens. A wide array of humoral and cellular immune mechanisms are present in the mammary gland and actively participate in providing immunity to newborns and the mammary gland per se. The acute inflammatory response is essential in determining the outcome of intramammary challenge, and factors affecting innate and adaptive immunity in the context of mammary health are reviewed in detail. The ruminant mammary gland is also unique in that lymphocyte trafficking, which is essential to adaptive immunity, is shared with the peripheral immune system rather than the common mucosal immune system.

Mannose receptor is a novel ligand for L-selectin and mediates lymphocyte binding to lymphatic endothelium

Continuous lymphocyte recirculation between blood and lymphoid tissues forms a basis for the function of the immune system. Lymphocyte entrance from the blood into the tissues has been thoroughly characterized, but mechanisms controlling lymphocyte exit from the lymphoid tissues via efferent lymphatics have remained virtually unknown. In this work we have identified mannose receptor (MR) on human lymphatic endothelium and demonstrate its involvement in binding of lymphocytes to lymphatic vessels. We also show that the binding requires L-selectin, and L-selectin and MR form a receptor-ligand pair. On the other hand, L-selectin binds to peripheral lymph node addressins (PNAds) on high endothelial venules (HEVs) that are sites where lymphocytes enter the lymphatic organs. Interestingly, MR is absent from HEVs and PNAds from lymphatic endothelium. Thus, lymphocyte L-selectin uses distinct ligand molecules to mediate binding at sites of lymphocyte entrance and exit within lymph nodes. Taken together, interaction between L-selectin and MR is the first molecularly defined mechanism mediating lymphocyte binding to lymphatic endothelium.

Cytokines modulate endothelial cell intracellular signal transduction required for VCAM-1-dependent lymphocyte transendothelial migration

Vascular cell adhesion molecule-1 (VCAM-1) activates endothelial cell NADPH oxidase which catalyzes production of reactive oxygen species (ROS). This activity is required for VCAM-1-dependent lymphocyte migration. The focus of our study was to determine whether these VCAM-1-dependent functions are modulated by cytokines. TGF-beta1 or IFN-gamma pretreatment of mouse endothelial cell lines inhibited VCAM-1-dependent B and T cell transendothelial migration without affecting initial lymphocyte adhesion. Neutralizing anti-TGF-beta1 blocked the effects of TGF-beta1 pretreatment of endothelial cells, whereas addition of anti-TGF-beta1 after TGF-beta1 pretreatment of the endothelial cells did not block TGF-beta1-mediated inhibition. Neutralizing anti-IFN-gamma also blocked the inhibitory effects of IFN-gamma. TGF-beta1 and IFN-gamma blocked migration by inhibiting the VCAM-1-stimulated production of low levels of ROS (0.1-0.9 microM H2O2). These results demonstrate that both TGF-beta1 and IFN-gamma directly affect the endothelial cells' ability to promote lymphocyte migration. IL-4 had differing effects on T and B cells during transmigration. IL-4 augmented T cell migration across the endothelial cell lines but did not affect T cell adhesion. Conversely, IL-4 increased B cell adhesion to the endothelial cell lines without affecting migration. In summary, cytokines can directly modulate microvascular endothelial cell intracellular signaling, demonstrating a new level of cytokine regulation of lymphocyte diapedesis.

Systemic immunity and mucosal immunity are induced against human immunodeficiency virus Gag protein in mice by a new hyperattenuated strain of Listeria monocytogenes

Vaccines designed to control chronic infections by intracellular agents such as human immunodeficiency virus type 1 (HIV-1) require the induction of cell-mediated immune responses to rid the host of pathogen-infected cells. Listeria monocytogenes has characteristics that make it an attractive vaccine vector for use against such infections. Here we show that parenteral immunization with a new highly attenuated strain of this organism provided complete protection against systemic and mucosal challenges with a recombinant vaccinia virus expressing HIV-1 gag. Immunization also generated a strong, long-term memory cytotoxic-T-lymphocyte (CTL) response in spleen, mesenteric lymph nodes, and Peyer's patches directed against the gag protein. Oral immunization with this attenuated strain also produced complete, long-lasting protection against the recombinant virus but only against mucosal virus challenge. Curiously, oral immunization was associated with a transient CTL response in the three lymphoid tissues examined.

Immune surveillance of mammary tissue by phagocytic cells

The leukocytes in milk consist of lymphocytes, neutrophil polymorphonuclear leukocytes (PMN) and macrophages. Lymphocytes together with antigen-presenting cells function in the generation of an effective immune response. Lymphocytes can be divided into two distinct subsets, T- and B-lymphocytes, that differ in function and protein products. The professional phagocytic cells of the bovine mammary gland are PMN and macrophages. In the normal mammary gland macrophages are the predominate cells which act as sentinels to invading mastitis causing pathogens. Once the invaders are detected, macrophages release chemical messengers called chemoattractants that cause the directed migration of PMN into the infection. Migration of neutrophils into mammary tissue provides the first immunological line of defense against bacteria that penetrate the physical barrier of the teat canal. However, their presence is like a double-edged sword. While the PMN are phagocytosing and destroying the invading pathogens, they inadvertently release chemicals which induces swelling of secretory epithelium cytoplasm, sloughing of secretory cells, and decreased secretory activity. Permanent scarring will result in a loss of milk production. Resident and newly migrated macrophages help reduce the damage to the epithelium by phagocytosing PMN that undergo programmed cell death through a process called apoptosis. Specific ligands on the neutrophil surface are required for directed migration and phagocytosis. In response to infection, freshly migrated leukocytes express greater numbers of cell surface receptors for immunoglobulins and complement and are more phagocytic than their counterparts in blood. However, phagocytic activity rapidly decreases with continued exposure to inhibitory factors such as milk fat globules and casein in mammary secretions. Compensatory hypertrophy in non-mastitic quarters partially compensates for lost milk production in diseased quarters. Advances in molecular biology are making available the tools, techniques, and products to study and modulate host-parasite interactions. For example the cloning and expression of proteins that bind endotoxin may provide ways of reducing damaging effects of endotoxin during acute coliform mastitis. The successful formation of bifunctional monoclonal antibodies for the targeted lysis of mastitis causing bacteria represents a new line of therapeutics for the control of mastitis in dairy cows.

Intracranial paracrine interleukin-2 therapy stimulates prolonged antitumor immunity that extends outside the central nervous system

To explore the potential efficacy of local cytokine delivery against tumors in the central nervous system (CNS), C57BL6 mice were simultaneously given intracranial injections of tumor challenge and of irradiated B16F10 melanoma cells transduced to secrete interleukin-2 (IL-2). Intracranial IL-2 therapy generated antitumor responses capable of extending the survival of animals that received simultaneous intracranial tumor challenge either locally or at distant sites in the brain. Nontransduced melanoma cells had little effect. Animals that survived intracranial IL-2 therapy and tumor challenge showed prolonged survival compared with controls when challenged with a second tumor dose 70 days after initial treatment. In addition, animals that rejected intracranial tumors were also protected from tumor growth upon rechallenge at sites outside the CNS (i.e., subcutaneous tumor challenge). Conversely, identical or 10-fold larger doses of IL-2-transduced cells administered by subcutaneous injection failed to generate protection against intracranial tumor challenges. Elimination of T-cell and natural killer (NK) subsets using gene knockout mice and antibody-depletion techniques demonstrated that NK cells were most important for the initial antitumor response, whereas CD4+ T-cells were not necessary. These studies demonstrate that local IL-2 therapy in the brain not only generates an immediate local antitumor immune response, but also establishes long-term immunologic memory capable of eliminating subsequent tumor challenges within and outside of the CNS. Furthermore, the antitumor response to paracrine IL-2 in the brain differed significantly from that in the flank, suggesting that the intrinsic CNS cells involved in initiating immunity within the brain have different cytokine requirements from their peripheral counterparts.

Ingested interferon-alpha prevents allograft islet transplant rejection

BACKGROUND

Ingested interferon (IFN)-alpha is a biological response modifier in experimental autoimmune encephalomyelitis and multiple sclerosis, and prevents type 1 diabetes in nonobese diabetic mice. Islet transplantation possesses significant potential advantages over whole-gland transplantation because it is simple, may achieve insulin independence, and has clear advantages over exogenous insulin therapy. Therefore, we examined whether ingested IFN-alpha, administered to islet allograft recipients, could prevent islet allograft rejection.

METHODS

Recipient C3H mice (H2k) were made diabetic and either untreated or treated with 10-1000 international units (IU) of ingested murine IFN-alpha daily from day -7 through day +14 after transplantation for a total of 21 days. Seven days after diabetes induction, recipients received allograft islets isolated from C57BL.10 donors (H2b) under the kidney capsule and were followed for overt diabetes via elevated blood glucose.

RESULTS

Control recipients and recipients fed 1000 IU all became diabetic by day 13, whereas mice ingesting IFN-alpha had delayed rejection for up to 27 (10 IU) to 29 days (100 IU) after islet transplantation. Treatment of recipients of islet allografts with ingested IFN-alpha doubles the time period before rejection compared with control mice. The feeding period with daily IFN-alpha was doubled from 21 days to 42 days in total, 7 days before transplantation and 35 days after transplantation.

CONCLUSION

Treatment of recipients of islet allografts with prolonged ingested IFN-alpha prevents rejection in a subset of recipients. Ingested IFN-alpha may prevent rejection if given continuously after transplantation.

Immune-adhesion molecules in the prevention of allograft rejection and reperfusion injury

Control of the immune system is of indispensable importance for graft acceptance and function. Immunological changes in the graft before and after organ harvesting, the transplantation procedure itself and the organ recipients clinical state contribute to the immune response. Leukocyte trafficking [1] into a graft is regulated by various signal transducing molecules, which have been characterised during the past years. Ligand molecules on endothelial cells and in the organ parenchyma are the counterparts for leukocyte adhesion and tissue infiltration. The expression of these ligand molecules is regulated by soluble factors and cell-cell interactions [2]. The regulation of tissue inflammation and repair mechanisms involving components of the immune system therefore depends on a number of cell-surface interactions. The processes of intravascular adhesion, transmigration and infiltration by leukocytes and platelets are mainly mediated by receptor ligand interactions with target cells (cell-cell) and extracellular matrix proteins (cell-matrix). The main molecular families of adhesion receptor/ligand molecules have been identified. Today, we are still far from understanding this network of interactions. The numbers of molecules and factors involved are still increasing. This review summarises the currently available knowledge on the intervention in this system by monoclonal antibodies (mAbs), peptides and blocking agents. From this review, it is evident that further investigations are justified.

Adoptive transfer from interferon-alpha-fed mice is associated with inhibition of active experimental autoimmune encephalomyelitis by decreasing recipient tumor necrosis factor-alpha secretion

Ingested type I interferon (IFN) suppresses clinical relapse in murine chronic experimental autoimmune encephalomyelitis (EAE), inhibits clinical attacks more effectively than subcutaneous doses, and decreases the adoptive transfer of EAE. To determine whether splenocytes from IFN-fed donors were "suppressor-like" populations, donor SJL/J mice were immunized and fed with mock IFN-alpha or with IFN-alpha every other day for at least 4 weeks after initial clinical attack. Recipients of adoptively transferred CD8+ T cells from mock IFN-alpha-fed donors showed no clinical improvement of clinical disease compared with actively immunized controls. In contrast, recipients of adoptively transferred CD8+ T cells from IFN-alpha-fed donors showed decreased clinical disease compared with recipients of mock IFN-alpha-fed CD8+ T cells. To evaluate the mechanism of protection by donor CD8+ T cells and to determine if ingested IFN-alpha activates natural immunomodulatory cell populations, the authors used the acute EAE model and naïve-fed donor animals as sources of T cells and CD8+ T cells. Con A-activated spleen T cells from naïve nonimmunized mock IFN-alpha-fed donors inhibited actively induced disease and showed decreased recipient TNF-alpha secretion compared with recipients of T cells from mock IFN-fed mice. Donor activated spleen CD8+ T cells from naïve nonimmunized IFN-alpha-fed animals suppressed actively induced EAE in recipients and showed decreased IFN-gamma and TNF-alpha proinflammatory secretion. Decreased recipient TNF-alpha secretion correlates best with the disease protection from IFN-fed T and CD8+ T cells.

Differential regulation of CD4 lymphocyte recruitment between the upper and lower regions of the genital tract during Chlamydia trachomatis infection

Genital infection with Chlamydia trachomatis results in both the local recruitment of protective immune responses and an inflammatory infiltrate that may also participate in tubal pathology. As a beginning to understanding the etiology of immune system-mediated tubal pathology, we evaluated the regional recruitment of lymphocyte subsets to different areas of the female genital tract (GT) over the course of a murine infection with the mouse pneumonitis agent of Chlamydia trachomatis (MoPn). Using flow cytometric techniques we found that the CD4 lymphocyte subset was preferentially recruited to the upper GT (oviduct and uterine horn) over the lower GT (cervical-vaginal region) throughout the course of MoPn infection. The influx of CD4 cells also correlated with the expression of endothelial cell adhesion molecules (ECAMs) and in vitro lymphocyte adherence in the upper GT. Interestingly, the expression of ECAMs in the lower GT was not maintained longer than 7 days after infection, even in the presence of viable chlamydiae. Taken together, these data suggest that regulatory mechanisms of lymphocyte recruitment differ between the upper and lower regions of the GT and may influence the clearance of chlamydiae and the development of tubal pathology.

Evaluation of the prognostic value of serum soluble CD 44 in patients with breast cancer

The outcome of breast carcinoma is usually determined by multiple factors. Aberrant expression of the cell adhesion molecule CD 44 has been claimed to be associated with poor prognosis in various human malignancies. This study was designed to investigate any correlation between the soluble adhesion molecule CD 44 and the clinicopathologic variables and to evaluate the possible prognostic significance of soluble CD 44. Venous blood samples were preoperatively collected from 100 patients with invasive breast carcinoma. The serum levels of different soluble CD 44 molecules (CD 44 standard form and CD 44 splice variant V6) were measured with an enzyme immunoassay method. The data of primary tumor status, age, estrogen receptor status, lymph node status, histologic grading, distant metastases status, TNM staging, S-phase fraction, and ploidy pattern were collected and evaluated simultaneously with the serum levels of soluble CD 44 st and CD 44 V6. Twenty healthy subjects were used as the control group. The serum levels of soluble CD 44 st showed no significant elevation in patient group. The mean value of soluble CD 44 V6 in patient group was 269.2 +/- 94.3 ng/ml and that of the control group was 179.5 +/- 50.7 ng/ml; the difference was significant (p < 0.01). In multivariate analysis, distant metastasis (p < 0.05) and TNM staging (p < 0.01) appeared as independent factors regarding the significant higher serum levels of soluble CD 44 V6. Based on our preliminary results, preoperative serum soluble CD 44 V6 is closely related to distant metastases and TNM staging. The possible role of soluble CD 44 V6 in the prognostic value of breast carcinoma deserves further elucidation and evaluation with long-term patient follow-up.

Potential use of serum CD44 as an indicator of tumour progression in acute leukemia

CD44 is a widely expressed cell surface glycoprotein with various functions. This molecule is shed from the cell surface and released as a soluble molecule. High serum levels of CD44 have been demonstrated in some solid tumours. In this study we measured serum CD44 in 25 patients with acute leukemia, in 12 with bacterial infections, and in 13 normal controls. The levels of serum CD44 of patients with bacterial infections were significantly higher (mean 531.3+/-60.1 ng/ml, p<0.001) than those of normal controls (299. 0+/-115.4 ng/ml). Acute leukemia patients before treatment had almost four-fold higher levels of serum CD44 than normal controls (mean 1301.9+/-1384.6 ng/ml, p<0.01). Serum CD44 levels were correlated with clinical status. After treatment the serum CD44 levels significantly decreased, but they were still higher than in normal controls. Patients in complete remission all relapsed if serum CD44 levels were higher than 500 ng/ml (normal+2 SD) after chemotherapy. The serum CD44 levels were correlated with the absolute numbers of leukemic cells in peripheral blood. The results demonstrated that serum CD44 levels correlate well with the clinical status of acute leukemia, and such evaluation may provide a reliable tumour marker of acute leukemia.

Autoimmunity is a type I interferon-deficiency syndrome corrected by ingested type I IFN via the GALT system

Type I interferons (IFN-alpha/beta), products of the innate immune system, can modulate immune function whereas proinflammatory IFN-gamma (type II IFN), a product of the acquired immune system upregulates inflammation and enhances cell mediated immunity. We have proposed a unifying hypothesis of the origin of autoimmunity as a type I IFN immunodeficiency syndrome involving inadequate regulation of the acquired immune system product IFN-gamma by the IFN-alpha/beta innate immune system. The common theme of ingested type I IFNs in autoimmunity is inhibition of proinflammatory type II IFN systemically or at the target organ. In multiple sclerosis (MS) and insulin-dependent diabetes mellitus (IDDM) at the target organ, and in rheumatoid arthritis (RA) as a regulator of other proinflammatory cytokines, IFN-gamma is the nexus of inflammation in autoimmunity. Ingested type I IFNs counteract type II IFN, overcome the relative lack of type I IFN activity, and ameliorate autoimmunity. The administration of type I IFNs (IFN-alpha/beta) via the gut offers an exciting alternative to systemic application for overcoming the type I IFN immunodeficiency in autoimmunity. Successful use of ingested type I IFN in three separate prototypical autoimmune diseases suggests a broad antiinflammatory therapeutic profile for this technology.

Ingested interferon alpha induces Mx mRNA

We have demonstrated that ingested murine interferon alpha (IFN-alpha) suppressed clinical relapse in chronic relapsing experimental autoimmune encephalomyelitis (CR-EAE), decreased inflammation and suppressed the adoptive transfer of EAE, and is a biological response modifier in patients with multiple sclerosis. We examined the relative levels of the Mx mRNA signal using semiquantitative reverse transcription-polymerase chain reaction analysis on splenocytes from mice and peripheral blood mononuclear cells from man after IFN-alpha ingestion. Both mice and man demonstrated inducible levels of Mx mRNA after ingesting IFN-alpha. Murine spleen T cells and CD8(+)T cells also demonstrated upregulation of Mx mRNA. Murine whole splenocytes demonstrated upregulation of Mx mRNA after IFN-alpha ingestion of 10 and 100 U, but not after 0, 1000, 5000 U. Ingested IFN-alpha acts via established pathways of type 1 IFN signalling.

Differential Homing Commitments of Antigen-Specific T Cells After Oral or Parenteral Immunization in Humans

Animal experiments show that lymphocytes activated in the intestine circulate through mesenteric lymph nodes, lymphatics, and blood, returning to the gut. Homing into intestinal lamina propria is mediated by lymphocyte surface homing receptors, mainly the α4β7-integrin. We studied in humans whether intestinal T cells entering the blood upon antigenic activation would exhibit homing commitments to the gut. Volunteers were immunized with keyhole limpet hemocyanin (KLH) first orally and then parenterally or only parenterally, and the expression of α4β7 on T cells specific for KLH or tetanus toxoid was studied. Circulating T cells were depleted of α4β7+ cells by immunomagnetic selection. This depletion removed a significant proportion of the KLH-specific cells (mean decrease in proliferative response of 71%) in the orally immunized volunteers. No difference in the KLH-induced proliferation was found between the total and the α4β7-depleted populations in volunteers parenterally immunized with KLH, regardless of whether a preceding mucosal priming had taken place or not. In both immunization groups, the depletion of α4β7+ cells had no influence on the proliferative response to tetanus toxoid. We conclude that, in contrast to T cells activated by parenteral immunization, gut-derived T cells have preferential homing commitments to the gut. This commitment was no longer observed after a subsequent parenteral Ag administration. Besides showing that the site of Ag encounter determines the expression of homing receptors, the present study is the first to provide evidence for a circulation of newly activated Ag-specific intestinal T cells back to the gut in humans.

Homing potentials of circulating antibody-secreting cells after administration of oral or parenteral protein or polysaccharide vaccine in humans

The site of antigen encounter influences the Ig-distribution and homing potentials of circulating antibody-secreting cells (ASC) induced. After oral antigen administration, the majority ASC secrete the mucosal Ig-isotype, IgA, and all of them express the gut homing receptor (HR), alpha 4 beta 7, thus implying mucosal homing of these cells. Parenteral protein vaccine induces an IgG-dominated response with a low proportion of alpha 4 beta 7 expressing cells. However, a polysaccharide vaccine, even if administered parenterally, elicits an IgA-dominated response, hence suggesting homing to the mucosa. In order to study the influence of the nature of the antigen on the targeting of the ASC response, the present work compares the homing potentials of circulating ASC in humans after administration of an oral Salmonella Typhi Ty21a vaccine (antigen studied: O-9,12 polysaccharide), an oral recombinant cholera vaccine (antigen studied: cholera toxin B-subunit, CTB protein), a parenteral pneumococcal vaccine (antigen studied: Pnc capsular polysaccharide 19F) or a parenteral tetanus toxoid vaccine (antigen studied: TT protein). alpha 4 beta 7 was expressed on a higher proportion of ASC induced by oral O-9,12 (99%) and CTB (99%) than by parenteral Pnc (70%) or TT (63%). L-selectin, the peripheral lymph node HR, was expressed on a smaller proportion of ASC induced by O-9,12 (37%) or CTB (43%) than of those induced by Pnc (78%) or TT (81%). The results imply that even if the nature of the antigen has a profound effect on the Ig-distribution of the ASC response, it does not seem to influence the targeting of the response.

Expression of exon v6-containing CD44 isoforms is related to poor prognosis of acute myelocytic leukemia

CD44 is a cell surface glycoprotein with a number of isoforms generated by alternative splicing of ten 'variant' exons in humans. Variant exon 6-containing isoforms of CD44 (CD44v6) have been implicated in the metastatic potential of rat carcinoma cell lines. Human homologues of CD44v6 are expressed in several tumour types and are involved in their progression. In the present study, we examined the expression of CD44 mRNA in 20 acute myelocytic leukemias by semiquantitative RT-PCR analysis and assessed its prognostic value. In all leukemic cells the predominant isoform was the 'standard' form of CD44 (CD44H), and intense bands were found in eight cases. CD44v6 was expressed in 11 cases, although its levels and those of other variants containing exon v7 through to v10 were much lower than those of CD44H. Isoforms containing exon v4 or v5 could not be detected. The expression of CD44v6 correlated with the death rate from leukemia (p > 0.05), but was not related to other risk factors. On the other hand, the intense expression of CD44H did not correlate with the prognosis of leukemia. CD44v6 thus appears to be a marker for the poor prognosis of acute myelocytic leukemia.

The Memory B Cell Subset Responsible for the Secretory IgA Response and Protective Humoral Immunity to Rotavirus Expresses the Intestinal Homing Receptor, α4β7

Infection of mice with murine rotaviruses induces life-long immunity, characterized by high levels of IgA in the intestine and large numbers of rotavirus (RV)-specific Ab-secreting cells in gut-associated lymphoid tissues. Lymphocyte trafficking into gut-associated lymphoid tissues is mediated by interaction of the α4β7 integrin on lymphocytes with the vascular mucosal addressin cell adhesion molecule-1. To determine whether B cell memory for RV correlates with α4β7 expression, we transferred sorted B220+ phenotypically defined memory (IgD−α4β7high and IgD− α4β7−) and naive (IgD+α4β7+) splenocytes into recombination-activating gene-2 knockout mice (B and T cell-deficient) that were chronically infected with RV. Only mice receiving α4β7high memory (IgD−) B cells produced RV-specific IgA in the stool, cleared the virus, and were immune to reinfection. α4β7high (but not α4β7−) memory B cells from donors boosted as much as 7 mo previously also cleared the virus, indicating that α4β7high memory B cells maintain long term functional immunity to RV. Although only α4β7high memory cells provided mucosal immunity, α4β7− cells from recently boosted donor animals could generate RV-specific serum IgG, but, like naive (IgD+) B cells, were unable to induce viral clearance even 60 days after cell transfer. These data indicate that protective immunity for an intestinal pathogen, RV, resides in memory phenotype B cells expressing the intestinal homing receptor, α4β7.

The murine buccal mucosa is an inductive site for priming class I-restricted CD8+ effector T cells in vivo

The present study shows that Langerhans cells of the buccal mucosa and the skin share a similar phenotype, including in situ expression of MHC class II, the mannose receptor DEC-205 and CD11c, and absence of the costimulatory molecules B7.1, B7.2 and CD40 as well as Fas. Application of 2,4-dinitrofluorobenzene (DNFB) onto the buccal mucosa is associated with a rapid migration of dendritic cells (DC) to the epithelium and induction of B7.2 expression on some DC. Buccal sensitization with DNFB elicited a specific contact sensitivity (CS) in response to skin challenge, mediated by class I-restricted CD8+ effector T cells and down-regulated by class II-restricted CD4+ T cells, demonstrated by the lack of priming of class I-deficient mice and the enhanced response of class II-deficient mice, respectively. CS induced by buccal immunization is associated with priming of class I-restricted CD8+ effector T cells endowed with hapten-specific cytotoxic activity. Thus, the buccal epithelium is an inductive site, equivalent to the epidermis, for the generation of CS independent of CD4 help, and of cytotoxic T lymphocyte (CTL) responses mediated by class I-restricted CD8+ T cells. We propose that immunization through the buccal mucosa, which allows antigen presentation by epithelial DC efficient for priming systemic class I-restricted CD8+ CTL, may be a valuable approach for single-dose mucosal vaccination with subunit vaccines.

A pilot double-blind, randomized, and placebo-controlled study of orally administered IFN-alpha-n1 (Ins) in pediatric patients with measles

To determine the safety and effectiveness of low-dose oral interferon-alpha (IFN-alpha) against measles, 30 confined pediatric patients were prospectively and randomly assigned to either a placebo or an oral IFN-alpha group and observed daily for 14 days in a double-blind manner. The IFN patients received a daily sublingual dose of 200 IU of human lymphoblastoid IFN-alpha. The IFN-treated group showed shorter average duration of malaise (3.2 vs. 10.7 days, p < 0.0001), anorexia (3.1 vs. 6.7 days, p < 0.0001), and irritability (1.1 vs. 2.2 days, p < 0.01) and shorter duration of macular/maculopapular/papular lesions (4.3 vs. 8.2 days,p < 0.0001) and branny desquamation (4.6 vs. 5.8 days, p > 0.05) and shorter time for rash to become generalized (5.5 vs. 10.3 days, p < 0.0001). No hematologic, renal, or liver toxicities were noted. It, therefore, appears that low-dose oral human lymphoblastoid IFN-alpha used in this pilot study is both safe and effective in children with measles infection.

Identification of an N-acetylglucosamine-6-0-sulfotransferase activity specific to lymphoid tissue: an enzyme with a possible role in lymphocyte homing

BACKGROUND

The leukocyte adhesion molecule L-selection participates in the initial attachment of blood-borne lymphocytes to high endothelial venules (HEVs) during lymphocyte homing to secondary lymphoid organs, and contributes to leukocyte adhesion and extravasation in HEV-like vessels at sites of chronic inflammation. The L-selection ligands on lymph mode HEVs are mucin-like glycoproteins adorned with the unusual sulfated carbohydrate epitope, 6-sulfo sialyl Lewis x. Sulfation of this epitope on the N-acetylglucosamine (GlcNAc) residue confers high-avidity L-selection binding, and is thought to be restricted in the vasculature to sites of sustained lymphocyte recruitment. The GlcNAc-6-0 sulfotransferase that installs the sulfate ester may be a key modulator of lymphocyte recruitment to secondary lymphoid organs and sites of chronic inflammation and is therefore a potential target for anti-inflammatory therapy.

RESULTS

A GlcNAc-6-0-sulfotransferase activity was identified within porcine lymph nodes and characterized using a rapid, sensitive, and quantitative assay. We synthesized two unnatural oligosaccharide substrates, GlcNAc beta 1-->6Gal alpha-R and Gal beta 1-->4GlcNAc beta 1-->6Gal alpha-R, that incorporate structural motifs from the native L-selection ligands into an unnatural C-glycosyl hydrocarbon scaffold. The sulfotransferase incorporated greater than tenfold more sulfate into the disaccharide than the trisaccharide, indicating a requirement for a terminal GlcNAc. Activity across tissues was highly restricted to the HEVs within peripheral lymph node.

CONCLUSIONS

The restricted expression of the GlcNAc-6-0-sulfotransferase activity to lymph node HEVs strongly suggestions a role in the biosynthesis of L-selection ligands. In addition, similar sulfated epitopes are known to be expressed on HEV-like vessels of chronically inflamed tissues; indicating that this sulfotransferase may also contribute to inflammatory lymphocyte recruitment. We identified a concise disaccharide motif, GlcNAc beta 1-->6Gal alpha-R, that preserved both recognition and specificity determinants for the GlcNAc-6-0-sulfotransferase. The absence of activity on the trisaccharide Gal beta 1-->6Gal alpha-R indicates a requirement for a substrate with a terminal GlcNAc residue, suggesting that sulfation precedes further biosynthetic assembly of L-selection ligands.

Differential migration of Th1 and Th2 cells--implications for vaccine and infection studies

Most lymphocytes migrate continuously between the blood and lymphatic system. This migration does not occur randomly and shows some bias for specific tissue compartments. In particular, CD4+ memory T cells have been shown to preferentially migrate to either peripheral or mucosal lymph nodes depending on their site of origin. The selective migration of lymphocytes into lymph nodes is facilitated by the differential expression of adhesion molecules on the lymphocyte surface interacting with their respective ligands on endothelial cells lining the capillary vessels. The acquisition of these 'mucosal' or 'peripheral' homing receptors was thought to be dictated by the particular tissue site in which lymphocyte were activated. A large amount of recent experimentation has shown that memory T cells generated against infectious agents can have different functional phenotypes as determined by their cytokine secretion patterns. Two of these distinct functional phenotypes. Th1 and Th2 cells, are differentially induced in peripheral and mucosal lymph nodes and recent data has suggested that the observed tissue-specific migration of memory T cells may be determined by this functional phenotype rather than the site of activation. Data in support of this new hypothesis are presented in this paper. In addition, as both the functional and surface phenotype of lymphocytes is dependent on local hormonal and cytokine environments, lymphocyte migration patterns may be manipulated by vaccination and infection.

Antigen direction of specific T-cell clones into gingival tissues

This study was performed to investigate T-cell traffic to periodontal tissues during infection with a periodontal pathogen Actinobacillus actinomycetemcomitans (Aa). Rowett rat T-cell clones, A3 (CD4+ CD8-, alpha beta TCR+, NKRP-1-, specific to Aa) and G2 (CD4- CD8-, alpha beta TCR+, NKRP-1+, which reacts to Aa, Gram-negative and -positive bacteria), both expressed the same prominent adhesion molecules (LFA-1, VLA-4) to the same extent. Binding of both T-cell clones to rat endothelial cells in vitro was blocked by antibody to VLA-4. Rowett rats were infected with Aa and infused with Aa-stimulated, isogenic T-clone lymphocytes that had been labelled in vitro with 125IUdR. Radioactivity associated with recovery of clone A3, but not G2, was significantly elevated in the gingivae of infected rats, suggesting migration to infected animals' gingival tissues. Migration of radioactive Aa-specific A3 clone cells traced by autoradiography reached a maximum at 24 hr (1.2% of total lymphocytes as radiolabelled cells in infected gingiva versus 0.6% in noninfected), indicating an apparent antigen-directed retention in infected rats' gingival tissues. The G2 clone was not retained in the gingival tissues (0.20% of total lymphocytes as radiolabelled cells in infected gingiva versus 0.26% in non-infected). However, the possibility of A3 retention directed by inflammation or tissue-selective homing could not be excluded. In further experiments, other adoptively transferred T-clone lymphocytes [clones G23 (Th1) and F13 (Th2)] with specificity for the 29,000 MW outer membrane protein of Aa with the same prominent adhesion molecules could be recovered from rat gingivae previously challenged with this antigen. However, transferred T-clone lymphocytes [clone G26 (Th1)] with specificity for a different Aa antigen were not recovered. Therefore, the dynamics of cell entry into periodontal lesions vary for activated T lymphocytes with different antigenic specificities, indicating the significance of antigen in lymphocyte traffic to periodontal tissues.

Expression of the mucosal homing receptor alpha4beta7 correlates with the ability of CD8+ memory T cells to clear rotavirus infection

The integrin alpha4beta7 plays an important role in lymphocyte homing to mucosal lymphoid tissues and has been shown to define a subpopulation of memory T cells capable of homing to intestinal sites. Here we have used a well-characterized intestinal virus, murine rotavirus, to investigate whether memory/effector function for an intestinal pathogen is associated with alpha4beta7 expression. Alpha4beta7(hi) memory phenotype (CD44hi), alpha4beta7- memory phenotype, and presumptively naive (CD44(lo)) CD8+ T lymphocytes from rotavirus-infected mice were sorted and transferred into Rag-2 (T- and B-cell-deficient) recipients that were chronically infected with murine rotavirus. Alpha4beta7(hi) memory phenotype CD8+ cells were highly efficient at clearing rotavirus infection, alpha4beta7- memory cells were inefficient or ineffective, depending on the cell numbers transferred, and CD44(lo) cells were completely unable to clear chronic rotavirus infection. These data demonstrate that functional memory for rotavirus resides primarily in memory phenotype cells that display the mucosal homing receptor alpha4beta7.

Recruitment of circulating allergen-specific T lymphocytes to the lung on allergen challenge in asthma

BACKGROUND

In allergic subjects with asthma, the migration of CD4+ T cells to the lungs in the hours after allergen exposure may contribute to allergic inflammation in the target organ.

OBJECTIVE

We studied allergen-specific T cells from the peripheral blood and lungs of allergic subjects with asthma at baseline and after allergen challenge.

METHODS

In each patient, blood samples were taken 10 minutes before and 24 hours after the inhalation of a major sensitizing allergen. In vitro proliferation of peripheral blood CD4+ T cells specific for the same allergen used in the in vivo challenge was assessed. In one patient two Dermatophagoides pteronyssinus-specific T-cell clones (TCCs) were derived from peripheral blood, and their T-cell receptors were sequenced to determine their clonotypic determinants on the beta chains. The T-cell receptor determinants of the allergen-specific TCCs were sought in blood and bronchoalveolar lavage samples taken from this patient.

RESULTS

We found that allergen inhalation is followed by a decrement in the specific proliferation of peripheral CD4+ T cells to the same allergen used for bronchial provocation. In one patient the clonotypic determinants of two allergen-specific TCCs diminished in the peripheral blood, whereas they were simultaneously expanded in the lower respiratory tract.

CONCLUSION

Our data suggest that allergen-specific T cells are recruited from the peripheral blood to the bronchial lumen after allergen challenge.

Human and murine high endothelial venule cells phagocytose apoptotic leukocytes

Apoptotic cell death occurs during normal lymphocyte development and differentiation as well as following lymphocyte exposure to endogenous corticosteroids released during stress, malnutrition, and trauma. Recognition and engulfment of these apoptotic cells is important for the clearance of dying cells before they release potent inflammatory mediators into the vasculature or tissues. Phagocytosis of apoptotic cells is accomplished in part by macrophages. We report for the first time that apoptotic lymphocytes are also phagocytosed by high endothelial venule (HEV) cells. The murine HEV cell line mHEVa rapidly phagocytosed apoptotic lymphoid and myeloid cells with the greatest rate of phagocytosis occurring at 0-6 h. To confirm HEV cell interaction with apoptotic cells, we demonstrated that apoptotic human tonsil lymphocytes were phagocytosed by human tonsil HEV cells in primary cultures. Furthermore, we examined HEV cell phagocytosis in vivo. Mice were treated with a natural corticosterone (4-pregnene-11 beta,21-diol-3,20-dione) at levels detected during stress or malnutrition (93-180 micrograms serum cortisol/dl). At 4-12 h posttreatment, apoptotic lymphocytes were present inside vacuoles of HEV cells in axillary lymph node tissue sections, as determined by transmission electron microscopy. These data suggest that, in addition to macrophages, lymph node HEV cells also play a role in the removal of apoptotic lymphocytes. Moreover, since HEV cells are specialized endothelial cells that regulate lymphocyte migration into peripheral lymphoid tissues, they may provide an important checkpoint for clearance of apoptotic lymphocytes within the vasculature, as well as limiting entrance of nonfunctional lymphocytes into the lymph node.

Vascular adhesion protein 1 (VAP-1) mediates lymphocyte subtype-specific, selectin-independent recognition of vascular endothelium in human lymph nodes

Interactions between lymphocyte surface receptors and their ligands on vascular endothelial cells regulate the exit of lymphocytes from the circulation. Distinct subsets of mononuclear cells bind to high endothelial venules (HEVs) in different lymphoid organs to a different extent, but the molecular mechanisms behind this selectivity have remained poorly characterized. Here we show that vascular adhesion protein-1 (VAP-1) mediates subtype-specific binding of CD8-positive T cells and natural killer cells to human endothelium. VAP-1-dependent, oligosaccharide-dependent peripheral lymph node (PLN) HEV adhesion under shear was independent of L-selectin, P-selectin glycoprotein ligand 1, and alpha4 integrins, the known lymphocyte receptors involved in the initial recognition of endothelial cells. PLN HEV adhesion was also critically dependent on peripheral lymph node vascular addressins (PNAds), but lymphocyte L-selectin was absolutely required for PNAd binding. Most lymphocytes relied on both PNAd and VAP-1 in HEV binding. The overlapping function of L-selectin ligands and VAP-1 in PLN introduces a new control point into the lymphocyte extravasation process. Finally, intravital microscopy revealed that VAP-1 is involved in initial interactions between human lymphocytes and endothelial cells in inflamed rabbit mesenterial venules in vivo. In conclusion, VAP-1 is a novel contact-initiating ligand that discriminates between different subpopulations of mononuclear cells and is an appealing target for selective modulation of adhesion of CD8- and CD16-positive effector cells.

Decreased expression of ICAM-1 and its induction by tumor necrosis factor on breast-cancer cells in vitro

In order to study adhesion-molecule expression and its consequences for cellular recognition, the presence of adhesion molecules ICAM-1, VCAM-1, VLA-4, LFA-1, alpha, LFA-1 beta, LFA-3, beta1-integrin and beta3-integrin was studied on specimens from breast tissue by immunohistochemistry and on cells from breast cell lines propagated in vitro. Breast-cancer tissue and the breast-cancer cell lines MCF-7, SK-BR-3 and ZR-75-1 showed expression of ICAM-1 and VLA-4 significantly lower than that of benign breast cells or normal breast epithelium. Of various cytokines tested, including recombinant human (rh) interleukin-6 (IL-6), rh tumor necrosis factor alpha (TNF-alpha), interleukin 2 (IL-2), granulocyte/macrophage-colony-stimulating-factor (GM-CSF), interferon-alpha (IFN-alpha) and interferon-gamma (IFN-gamma), only TNF was able to re-induce expression of ICAM-1 on cells from MCF-7, SK-BR-3 and ZR-75-1. Further, the ability of either unstimulated or lymphokine-stimulated killer (LAK) cells to recognize and lyse native or TNF-stimulated breast-cancer cells was studied. Whereas neither unstimulated lymphocytes or LAK cells were able to lyse untreated breast-cancer cells deficient for ICAM-1 expression, pre-treatment of tumor cells with TNF led to increased tumor-cell lysis. Anti-ICAM-1 antibodies, and pre-treatment of tumor cells with anti-TNF-receptor antibodies, abrogated these findings, corroborating their specificity. We thus conclude that the defective expression of ICAM-1 in our model might constitute a mechanism by which breast-cancer cells escape immunologic recognition and lysis by appropriate effector cells.