A survey of professional activities of psychiatrists in South Africa

Targeted inactivation of genes in the tumor necrosis factor (TNF)/lymphotoxin (LT) ligand and receptor system has recently revealed essential roles forthese molecules in lymphoid tissue development and organization. Lymphotoxin-alpha beta (LT alpha beta)/lymphotoxin-beta receptor (LT beta-R) signaling is critical for the organogenesis of lymph nodes and Peyer's patches and for the structural compartmentalization of the splenic white pulp into distinct B and T cell areas and marginal zones. Moreover, an essential role has been demonstrated for TNF/p55 tumor necrosis factor receptor (p55TNF-R) signaling in the formation of splenic B lymphocyte follicles, follicular dendritic cell networks, and germinal centers. In contrast to a previously described essential role for the p55TNF-R in Peyer's patch organogenesis, we show in this report that Peyer's patches are present in both TNF and p55TNF-R knockout mice, demonstrating that these molecules are not essential for the organogenesis of this lymphoid organ. Furthermore, we show that in the absence of TNF/p55TNF-R signaling, lymphocytes segregate normally into T and B cell areas and a normal content and localization of dendritic cells is observed in both lymph nodes and Peyer's patches. However, although B cells are found to home normally within Peyer's patches and in the outer cortex area of lymph nodes, organized follicular structures and follicular dendritic cell networks fail to form. These results show that in contrast to LT alpha beta signaling, TNF signaling through the p55TNF-R is not essential for lymphoid organogenesis but rather for interactions that determine the cellular and structural organization of B cell follicles in all secondary lymphoid tissues.     

Mast cell activation and migration to lymph nodes during induction of an immune response in mice

The mast cell response in skin and lymph nodes was examined during the sensitization phase of dinitrofluorobenzene (DNFB)-induced contact hypersensitivity in mice. Degranulation of 62% of mast cells in DNFB-exposed skin was evident within 30 min of a dual application of DNFB, reaching a peak of 77% at 24 h, and persisting in 42% after 5 d. Abundant expression of macrophage inflammatory protein (MIP)-1alpha and MIP-1beta mRNAs and proteins was observed in keratinocytes, and mast cell degranulation was significantly inhibited after administration of neutralizing antibodies to MIP-1alpha, but not MIP-1beta. During DNFB sensitization, the mast cell density in the skin decreased by half, concurrent with a fivefold expansion of mast cell numbers in draining lymph nodes. Fluorescent-labeled mast cells injected into the skin appeared in draining lymph nodes after application of DNFB, followed by subsequent migration to the spleen. In lymph nodes, mast cells were an abundant and predominant source of MIP-1beta, neutralization of which partially inhibited T lymphocyte recruitment. These results indicate that mast cells contribute to the induction of this primary immune response by activation at and migration from the site of antigen encounter to draining lymph nodes, wherein they mediate T lymphocyte recruitment by production of MIP-1beta.     

High expression level of alpha 6 integrin in human breast carcinoma is correlated with reduced survival

We recently reported that alpha 6 integrin mediates experimental metastasis in mice by functioning in the adhesion of tumor cells to the vascular endothelium. In the current study, we investigated the expression of human alpha 6 integrin in invasive breast carcinomas of 119 women. In 50% of the tumors alpha 6 integrin was expressed in the majority of the cells, and this expression was correlated with reduced survival time. By contrast, the 24% of patients with breast tumors devoid of alpha 6 integrin expression all survived. The tumors were also evaluated for clinical risk factors including histological grading and steroid receptor level. The combination of these factors with alpha 6 integrin expression was superior in predicting overall survival than considering the other factors alone. The correlation with decreased survival time was consistent, regardless of whether the tumors expressed the alpha 6 integrin A or B forms, which differ in their cytoplasmic domain. On the basis of this pilot study we consider alpha 6 integrin expression to be a novel prognostic marker for human breast cancer.     

Integrin alpha 6A beta 1 induces CD81-dependent cell motility without engaging the extracellular matrix migration substrate

It is well established that integrins and extracellular matrix (ECM) play key roles in cell migration, but the underlying mechanisms are poorly defined. We describe a novel mechanism whereby the integrin alpha 6 beta 1, a laminin receptor, can affect cell motility and induce migration onto ECM substrates with which it is not engaged. By using DNA-mediated gene transfer, we expressed the human integrin subunit alpha 6A in murine embryonic stem (ES) cells. ES cells expressing alpha 6A (ES6A) at the surface dimerized with endogenous beta 1, extended numerous filopodia and lamellipodia, and were intensely migratory in haptotactic assays on laminin (LN)-1. Transfected alpha 6A was responsible for these effects, because cells transfected with control vector or alpha 6B, a cytoplasmic domain alpha 6 isoform, displayed compact morphology and no migration, like wild-type ES cells. The ES6A migratory phenotype persisted on fibronectin (Fn) and Ln-5. Adhesion inhibition assays indicated that alpha 6 beta 1 did not contribute detectably to adhesion to these substrates in ES cells. However, anti-alpha 6 antibodies completely blocked migration of ES6A cells on Fn or Ln-5. Control experiments with monensin and anti-ECM antibodies indicated that this inhibition could not be explained by deposition of an alpha 6 beta 1 ligand (e.g., Ln-1) by ES cells. Cross-linking with secondary antibody overcame the inhibitory effect of anti-alpha 6 antibodies, restoring migration or filopodia extension on Fn and Ln-5. Thus, to induce migration in ES cells, alpha 6A beta 1 did not have to engage with an ECM ligand but likely participated in molecular interactions sensitive to anti-alpha 6 beta 1 antibody and mimicked by cross-linking. Antibodies to the tetraspanin CD81 inhibited alpha 6A beta 1-induced migration but had no effect on ES cell adhesion. It is known that CD81 is physically associated with alpha 6 beta 1, therefore our results suggest a mechanism by which interactions between alpha 6A beta 1 and CD81 may up-regulate cell motility, affecting migration mediated by other integrins.     

Distinct alpha 7A beta 1 and alpha 7B beta 1 integrin expression patterns during mouse development: alpha 7A is restricted to skeletal muscle but alpha 7B is expressed in striated muscle, vasculature, and nervous system

The laminin binding alpha 7 beta 1 integrin has been described as a major integrin in skeletal muscle. The RNA coding for the cytoplasmic domain of alpha 7 integrin undergoes alternative splicing to generate two major forms, denoted alpha 7A and alpha 7B. In the current paper, we have examined the developmental expression patterns of the alpha 7A and alpha 7B splice variants in the mouse. The alpha 7 integrin expression is compared to that of the nonintegrin laminin receptor dystroglycan and to that of laminin-alpha 1 and laminin-alpha 2 chains. Alpha 7A integrin was found by in situ hybridization to be specific to skeletal muscle. Antibodies specific for alpha 7B integrin and in situ hybridization revealed the presence of alpha 7 mRNA and alpha 7B protein in the E10 myotome and later in primary and secondary myotubes. In the heart, alpha 7B integrin was not detectable in the endocardium or myocardium during embryonic and fetal heart development. Northern blot analysis and immunohistochemistry revealed a postnatal induction of alpha 7B in the myocardium. In addition to striated muscle, alpha 7B integrin was localized to previously unreported nonmuscle locations such as a subset of vascular endothelia and restricted sites in the nervous system. Comparison of the alpha 7 integrin expression pattern with that of different laminin isoforms and dystroglycan revealed a coordinated temporal expression of dystroglycan, alpha 7 integrin, and laminin-alpha 2, but not laminin-alpha 1, in the forming skeletal muscle. We conclude that the alpha 7A and alpha 7B integrin variants are expressed in a developmentally regulated, tissue-specific pattern suggesting different functions for the two splice forms.     

Molecular cloning, functional characterization and mRNA expression analysis of the murine chemokine receptor CCR6 and its specific ligand MIP-3alpha

We have cloned the murine CCR6 receptor and its ligand, the beta-chemokine mMIP-3alpha. Calcium mobilization assays performed with mCCR6 transfectants showed significant responses upon addition of mMIP-3alpha. Murine MIP-3alpha RNA is expressed in thymus, small intestine and colon, whereas mCCR6 RNA is expressed in spleen and lymph nodes. RT-PCR analysis of FACS-sorted lymphoid and antigen presenting cell subsets showed mCCR6 expression mainly in B cells, CD8- splenic dendritic cells and CD4+ T cells. The cloning and functional characterization of the mCCR6 and mMIP-3alpha will allow the study of the role of these proteins in mouse models of inflammation and immunity.     

Regulation of T lymphocyte trafficking into lymph nodes during an immune response by the chemokines macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta

By virtue of their target cell specificity, chemokines have the potential to selectively recruit leukocyte subpopulations into sites of inflammation. Their role in regulation of T lymphocyte traffic into lymph nodes during the development of an immune response has not previously been explored. The sensitization phase of contact hypersensitivity induced by the hapten, dinitrofluorobenzene (DNFB) in the mouse was used as a model of T lymphocyte trafficking in response to antigenic stimulation. Rapid accumulation of CD8+ and CD4+ T cells in the draining lymph nodes was closely associated with strongly enhanced expression of macrophage inflammatory protein (MIP)-1 alpha and MIP-1 beta mRNAs and proteins. Mast cells accumulating in the nodes during DNFB sensitization were the predominant source of MIP-1 beta, whereas MIP-1 alpha was expressed by multiple cell types. Neutralization of these chemokines profoundly inhibited T lymphocyte trafficking into lymph nodes and altered the outcome of a subsequent challenge to DNFB. Thus, beta-chemokines regulate T lymphocyte emigration from the circulation into lymph nodes during an immune response and contribute significantly to the immunologic outcome.     

Differential requirements for alpha4 integrins during fetal and adult hematopoiesis

Mice chimeric for the expression of alpha4 integrins were used to dissect the roles of these receptors in development and traffic of lymphoid and myeloid cells. During fetal life, T cell development is alpha4 independent, but after birth further production of T cells becomes alpha4 dependent. Precursors for both T and B cells require alpha4 integrins for normal development within the bone marrow. In contrast, monocytes and natural killer cells can develop normally without alpha4 integrins. Thus, there are lymphocyte-specific, developmentally regulated requirements for alpha4 integrins in hematopoiesis in the bone marrow. We also show that alpha4 integrins are essential for T cell homing to Peyer's patches, but not to other secondary lymphoid organs, including spleen, lymph nodes, and intestinal epithelium.     

Distribution of extracellular and cytoplasmic domains of the alpha 3 and alpha 6 integrin subunits in solid tumors

Integrins play an important role in malignant transformation and the invasion of tumors. They mediate cell-cell and cell-matrix interactions and participate in transduction of signals across the plasma membrane, processes dependent on the extracellular and cytoplasmic domains of integrins. We studied a selection of solid tumors by immunohistochemistry using monoclonal antibodies (MAbs) against the extracellular domain and the cytoplasmic variants (A and B) of the alpha 3 and alpha 6 integrin subunits. The tissue-specific expression of ecto- and cyto-domains of alpha 3 and alpha 6 is maintained in a subset of breast, colon, kidney and parotid tumors. In a few breast tumors, there was a switch in variant expression in that alpha 6B was detected instead of alpha 6A in normal breast tissue. In many colon and parotid tumors, one of the variants of alpha 6 was missing, while both were detectable in the corresponding normal tissues. In contrast, coexpression of the alpha 6 variants was found in some kidney tumors, whereas only one of the variants was detected in the normal tissue. In a minority of colon and kidney tumors, the cyto-domains of alpha 3 and alpha 6 were undetectable and total absence of alpha 3 and alpha 6 was noted in a subset of breast, colon, kidney and parotid tumors. These observations show that expression of the integrin variants in tumors varies considerably and support the concept that changes in expression may contribute to malignant behavior.     

Catecholamine modulation of lymphocyte homing to lymphoid tissues

Lymphocyte migration is an essential process for immune surveillance and for promoting cell-cell interactions necessary to generate an immune response. This report examined whether catecholamine prestimulation would alter the pattern of lymphocyte homing to spleen and lymph nodes in mice as determined by tracking fluorescently labeled cells. The results of cell sorter analysis showed that catecholamine-pretreated cells had increased accumulation in spleen and lymph nodes 1 and 2 h after i.v. injection. In addition, microscopic analysis showed that labeled cells migrated from the splenic red pulp to T-cell regions of the white pulp over a 2-h time course. Within the lymph nodes, labeled cells localized predominantly to the pericortex. Additional studies examined the migration of lymphocytes to lymphoid tissues of NGF-transgenic mice that have sympathetic hyperinnervation of spleen and peripheral lymph nodes. In contrast to the studies above, migration of T-cells from control mice to lymphoid tissues of the hyperinnervated mice was not different than that in control mice in most tissues. The accumulation of lymphocytes in lymphoid tissues is a balance between the influx of newly migrated cells and efflux back into the circulation. The studies in this report lend support to other studies showing catecholamine modulation of lymphocyte migration and homing, but it is a complex process about which much has yet to be understood.     

Novel splice variants of the voltage-sensitive sodium channel alpha subunit

In this study, we have identified novel splice variants of the Na+ channel alpha subunit mRNA from cultured rat astrocytes and neuroblastoma cells. These splice variants are characterized by premature truncation or deletion of a segment in the third domain of the Na+ channel alpha subunit. The expression of three splice variants was upregulated by exposure to 1 mM dibutyryl cAMP in spinal cord astrocytes but not in cerebral astrocytes and in B50 and B104 neuroblastoma cells. The calcium ionophore 1 microM A23187, did not influence the expression of splice variants in either astrocytes or neuroblastoma cells. These findings suggest that spinal cord astrocytes may maintain a unique regulatory pathway that participates in the control of Na+ channel mRNA expression.     

ATP-induced, P2U purinoceptor-mediated constriction of isolated, perfused mesenteric beds of the rat

Upon antigen encounter epidermal Langerhans cells (LC) and dendritic cells (DC) emigrate from peripheral organs and invade lymph nodes through the afferent lymphatic vessels and then assemble in the paracortical T cell zone and present antigen to T lymphocytes. Part of this process is mimicked by metastasizing tumor cells. Since splice variants of CD44 promote metastasis to lymph nodes we explored the expression of CD44 proteins on migrating LC and DC. We show that following antigen contact, LC and DC upregulate pan CD44 epitopes and epitopes encoded by variant exons v4, v5, v6 and v9. Antibodies against CD44 epitopes arrest LC in the epidermis, prevent the binding of activated LC and DC to the T cell zones of lymph nodes, and severely inhibit their capacity to induce a delayed type hypersensitivity reaction to a skin hapten in vivo. Our results demonstrate that CD44 splice variant expression is obligatory for the migration and function of LC and DC.     

A dose proportionality study of eprosartan in healthy male volunteers

BACKGROUND: Previous investigations in BALB/c strain mice have revealed that, after skin sensitization, draining lymph node cells (LNC) produce high levels of interleukin 6 (IL-6) and that the secretion of this cytokine correlates closely with the proliferative activity of LNC. The main source of IL-6 within draining lymph nodes was found to be dendritic cells (DC), most of which derive from epidermal Langerhans cells. OBJECTIVE: To explore further the relationship between DC-derived IL-6 production in lymph nodes, LNC proliferative activity, and the development of contact sensitization, comparisons between BALB/c and C3H/HeN strains of mice have been conducted. METHODS: Contact sensitizing potential was measured in both strains of mice as a function of lymphocyte proliferative responses (assessed by the incorporation of radiolabelled thymidine) and challenge-induced increases in ear thickness. The concentration of IL-6 in skin homogenates and the production of IL-6 by allergen-activated LNC were measured by enzyme-linked immunosorbent assay (ELISA). RESULTS: In both strains of mouse, topical exposure to oxazolone, a potent contact allergen, induced a vigorous proliferative response by draining LNC and the development of skin sensitization. However, under these conditions of exposure, activated LNC prepared from mice of C3H/HeN strain failed to secrete substantial amounts of IL-6, the levels of this cytokine being on average some 20- to 40-fold less than those measured in BALB/c mice. The failure of LNC from C3H/HeN mice to secrete comparable levels of IL-6 was not attributable to a reduced ability of DC to accumulate in draining lymph nodes after skin sensitization. Nor did reduced IL-6 secretion by C3H/HeN LNC reflect a systemic inability to elaborate this cytokine. Epicutaneous exposure of C3H/HeN mice to oxazolone resulted in the induction of cutaneous IL-6 at levels similar to, or greater than, those observed after identical treatment of BALB/c strain mice. CONCLUSIONS: The conclusion drawn is that there does not exist a universal association between IL-6 production in draining lymph nodes and the vigor of proliferative responses by LNC. Further, cutaneous immune responses and skin sensitization may proceed apparently normally in the absence of high levels of IL-6 production by lymph node cells.     

Evidence that macrophages are required for T-cell infiltration and rejection of fetal pig pancreas xenografts in nonobese diabetic mice

BACKGROUND: Host macrophages are abundant within fetal pig pancreas xenografts undergoing rejection, but their role is unknown. Therefore, we examined the effect of host macrophage depletion on xenograft rejection. METHODS: Nonobese diabetic (NOD) mice were given clodronate-loaded liposomes intravenously to deplete macrophages. Controls received phosphate-buffered saline (PBS) or PBS-liposomes. General immune status was assessed after 2, 3, and 7 days by (1) fluorescence-activated cell sorter analysis of peripheral blood, spleen, and lymph node cells, (2) immunohistochemistry on spleens, and (3) mixed lymphocyte reaction. Organ-cultured fetal pig pancreas was transplanted under the kidney capsule of NOD mice 3 days after clodronate or PBS injection. Grafts were assessed histologically at 4, 5, 6, and 8 days after transplantation. RESULTS: Splenic macrophages and peripheral blood monocytes were depleted 2 days after clodronate treatment but had recovered within 11 days. T cell, B cell, and dendritic cell numbers were normal in spleen, peripheral blood, and lymph nodes of clodronate-treated mice, and T cells and antigen-presenting cells from these mice functioned normally in mixed lymphocyte reaction. Clodronate treatment markedly reduced graft infiltration by macrophages, T cells, and eosinophils at 4, 5, and 6 days after transplantation, and was associated with maintenance of endocrine cell viability and insulin expression. However, all grafts were rejected 8 days after transplantation, concordant with reappearance of splenic macrophages. CONCLUSIONS: Short-term, specific depletion of macrophages markedly delayed cellular infiltration and rejection of xenografts. The results provide the first evidence that macrophages promote T-cell infiltration and rejection of fetal pig pancreas xenografts in NOD mice.     

Depressed Langerhans cell migration and reduced contact hypersensitivity response in mice lacking TNF receptor p75

Epidermal Langerhans cells (LC) belong to the dendritic cell family and represent the major APC within the skin. LC capture epicutaneous Ag, migrate into regional lymph nodes, and present Ag to T cells, thereby initiating primary immune response. The migratory properties of LC are an essential component of their function. The molecular mechanisms responsible for LC migration are far less defined. However, evidence has been accumulating to suggest that TNF-alpha, a major proinflammatory cytokine, plays an important role in promoting DC migration. To confirm the role of TNF-alpha in LC migration and to examine which type of TNF receptor signaling is involved in such an event, we utilized gene-targeted knockout mice lacking TNF receptor p55 or p75. The migration of LC was assessed by examining the frequency of hapten-bearing cells in draining lymph nodes following hapten FITC painting, and the accumulation of dendritic cells in draining lymph nodes after intradermal injection of TNF-alpha. While LC migration was normal in p55-deficient mice, the migration was markedly depressed in p75-deficient mice. Receptor p75-deficient mice also demonstrated a hyporesponsiveness in allergen-induced contact dermatitis, but a normal responsiveness in irritant-induced contact dermatitis. These results suggest that p75-dependent signaling plays a crucial role in the migration of LC and in the initiation of cutaneous immune responses.     

Secondary lymphoid-tissue chemokine (SLC) stimulates integrin alpha 4 beta 7-mediated adhesion of lymphocytes to mucosal addressin cell adhesion molecule-1 (MAdCAM-1) under flow

The attachment of leukocytes to the endothelium is a multistep process that depends upon a very rapid increase in the adhesive activity of leukocyte integrins. A pertussis toxin-sensitive pathway stimulates integrin-dependent lymphocyte adhesion to Peyer's patch high endothelial venules in vivo, but the factors responsible for activating this pathway have not been identified previously. We now report that secondary lymphoid-tissue chemokine (SLC) (also known as 6Ckine, Exodus-2, and thymus-derived chemotactic agent 4), a recently described CC chemokine that is expressed in Peyer's patches and lymph nodes, rapidly activates integrin-mediated lymphocyte adhesion. Immobilized SLC increased the adhesion of HUT-78 T cells and human PBLs to mucosal addressin cell adhesion molecule-1, a protein that is expressed on Peyer's patch and mesenteric lymph node high endothelial venules. This effect of SLC was seen in both static and flow chamber adhesion assays, was mediated by integrin alpha 4 beta 7, and was inhibited by pertussis toxin. The other CC chemokines tested did not increase adhesion to mucosal addressin cell adhesion molecule-1. SLC had a greater effect on naive CD4+ T cells than on memory CD4+ T cells; CD8+ T cells, B cells, and NK cells were also responsive to SLC. SLC is likely to play an important role in regulating the recruitment of lymphocytes to Peyer's patches and lymph nodes.     

Integrin alpha 6 beta 4 forms a complex with the cytoskeletal protein HD1 and induces its redistribution in transfected COS-7 cells

The integrin alpha 6 beta 4 is a major component of hemidesmosomes, in which it is linked to intermediate filaments. Its presence in these structures is dependent on the beta 4 cytoplasmic domain but it is not known whether beta 4 interacts directly with keratin filaments or by interaction with other proteins. In this study, we have investigated the interaction of GST-cyto beta 4A fusion proteins with cellular proteins and demonstrate that a fragment of beta 4A, consisting of the two pairs of fibronectin type III repeats, separated by the connecting segment, forms a specific complex containing a 500-kDa protein that comigrates with HD1, a hemidesmosomal plaque protein. A similar protein was also bound by a glutathione S-transferase fusion protein containing the cytoplasmic domain of a variant beta 4 subunit (beta 4B), in which a stretch of 53 amino acids is inserted in the connecting segment. Subsequent immunoblot analysis revealed that the 500-kDa protein is in fact HD1. In COS-7 cells, which do not express alpha 6 beta 4 or the hemidesmosomal components BP230 and BP180, HD1 is associated with the cytoskeleton, but after transfecting the cells with cDNAs for human alpha 6 and beta 4, it was, instead, colocalized with alpha 6 beta 4 at the basal side of the cells. The organization of the vimentin, keratin, actin, and tubulin cytoskeletal networks was not affected by the expression of alpha 6 beta 4 in COS-7 cells. The localization of HD1 at the basal side of the cells depends on the same region of beta 4 that forms a complex containing HD1 in vitro, since the expression of alpha 6 with a mutant beta 4 subunit that lacks the four fibronectin type III repeats and the connecting segment did not alter the distribution of HD1. The results indicate that for association of alpha 6 beta 4 with HD1, the cytoplasmic domain of beta 4 is essential. We suggest that this association may be crucial for hemidesmosome assembly.     

Sulcotrione soil metabolism in summer corn crops

The IL-15 receptor alpha subunit (IL-15Ralpha) mediates high-affinity binding of IL-15, a pleiotropic cytokine implicated in the development of innate immune cells. We have generated IL-15Ralpha null (IL-15Ralpha-/-) mice to understand the role of IL-15Ralpha in immune development and function. IL-15Ralpha-/- mice are markedly lymphopenic despite grossly normal T and B lymphocyte development. This lymphopenia is due to decreased proliferation and decreased homing of IL-15Ralpha-/- lymphocytes to peripheral lymph nodes. These mice are also deficient in natural killer cells, natural killer T cells, CD8+ T lymphocytes, and TCRgammadelta intraepithelial lymphocytes. In addition, memory phenotype CD8+ T cells are selectively reduced in number. Thus, IL-15Ralpha has pleiotropic roles in immune development and function, including the positive maintenance of lymphocyte homeostasis.     

Efficient lymphocyte migration across high endothelial venules of mouse Peyer's patches requires overlapping expression of L-selectin and beta7 integrin

Lymphocyte migration into lymphoid organs is regulated by adhesion molecules including L-selectin and the beta7 integrins. L-selectin and alpha4beta7 are predominantly hypothesized to direct the selective migration of lymphocytes to peripheral lymph nodes and the gut-associated lymphoid tissues, respectively. To further characterize interactions between L-selectin and beta7 integrins during lymphocyte recirculation, mice deficient in both receptors (L-selectin/beta7 integrin-/-) were generated. The simultaneous loss of L-selectin and beta7 integrin expression prevented the majority of lymphocytes (>95% inhibition) from attaching to high endothelial venules (HEV) of Peyer's patches and other lymphoid tissues during in vitro binding assays. Moreover, the inability to bind HEV eliminated the vast majority of L-selectin/beta7 integrin-/- lymphocyte migration into Peyer's patches during short-term and long-term in vivo migration assays (>99% inhibition,p < 0.01). The lack of lymphocyte migration into Peyer's patches correlated directly with the dramatically reduced size and cellularity (99% reduced) of this tissue in L-selectin/beta7 integrin-/- mice. High numbers of injected L-selectin/beta7 integrin-/- lymphocytes remaining in the blood of wild-type mice correlated with markedly increased numbers of circulating lymphocytes in L-selectin/beta7 integrin-/- mice. Loss of either L-selectin or the beta7 integrins alone resulted in significant but incomplete inhibition of Peyer's patch migration. Collectively, the phenotype of L-selectin/beta7 integrin-/- mice demonstrates that these two receptors primarily interact along the same adhesion pathway that is required for the vast majority of lymphocyte migration into Peyer's patches.