Mucosal High Endothelial Venules Research Articles

Function of lymphocyte homing-associated adhesion molecules on human natural killer and lymphokine-activated killer cells.

We have analyzed the ability of fresh and rIL-2-activated human NK cells to interact with high endothelial venules (HEV) that are known to support physiologic lymphocyte extravasation, and examined the role of different adhesion molecules in this process. In in vitro HEV-binding assays, NK cells bound to both peripheral lymph node (pLN) and mucosal HEV. Activation by rIL-2 slightly decreased adherence to pLN HEV, but increased adherence to mucosal high endothelium. Markedly fewer NK cells than PBL expressed L-selectin, and the expression was diminished further upon treatment with rIL-2. Inhibition studies showed, however, that L-selectin was the most important single molecule to mediate adhesion to pLN HEV. Binding to mucosal HEV was mediated mainly by CD44 and alpha 4 integrin, and the expression level of these molecules was increased by rIL-2, paralleling the results in HEV-binding assays. Higher m.w. forms of CD44, representing differentially glycosylated/variant forms of CD44, were more abundant on large granular lymphocytes than on unseparated PBL. We conclude that, despite weak recirculatory capacity, NK cells or a subpopulation of NK cells with the correct adhesion molecules can interact with and bind to high endothelial cells. Lymphokines can modulate the expression of adhesion molecules that NK cells utilize for HEV binding. Our results suggest that activation of NK cells with IL-2 may facilitate the extravasation of lymphokine-activated killer cells, especially to mucosal sites, whereas homing to peripheral lymphoid tissues may be diminished. This should be taken into consideration when procedures for lymphokine-activated killer cell immunotherapy are planned.

Dual binding capacity of mucosal immunoblasts to mucosal and synovial endothelium in humans: dissection of the molecular mechanisms.

Lymphocytes continuously migrate throughout the body in search of antigens. Virgin lymphocytes recirculate freely between the blood and different lymphatic organs, whereas immunoblasts extravasate preferentially into sites similar to those where they initially responded to antigen. Tissue-specific extravasation of lymphocytes is largely controlled by distinct lymphocyte surface receptors that mediate lymphocyte binding to high endothelial venules (HEV). In the present study, the molecular mechanisms determining the specificity of human mucosal (lamina propria) lymphocyte binding to different endothelial recognition systems were analyzed. Mucosal immunoblasts adhered five times better than small mucosal lymphocytes to mucosal HEV. Importantly, mucosal immunoblasts also bound to synovial HEV almost as efficiently as to mucosal HEV, but they did not adhere to peripheral lymph node HEV. To study the impact of different homing-associated molecules in this dual endothelial binding, we used a gut-derived T cell line and freshly isolated mucosal immunoblasts. Both cell types expressed integrins alpha 4, beta 1, beta 7, and lymphocyte function associated antigen 1 (LFA-1), and were CD44 positive, but practically L-selectin negative. Binding of mucosal immunoblasts to mucosal HEV was almost completely abolished by pretreatment with anti-beta 7 monoclonal antibodies, but it was independent of alpha 4/beta 1 function. In contrast, alpha 4/beta 1 partially mediated immunoblast adherence to synovial HEV, whereas alpha 4/beta 7 had only a minor role in adherence of blasts at this site. CD44 and LFA-1 contributed to HEV-binding both in mucosa and synovium. Taken together, this is the first report that demonstrates a critical role for alpha 4/beta 7 in the binding of gut lymphocytes to mucosal venules in humans. Moreover, a hitherto unknown interaction between mucosal effector cells and synovial endothelial cells was shown to be only partially mediated by the currently known homing receptors. The dual endothelial binding capacity of mucosal blasts may help to explain the pathogenesis of reactive arthritis not uncommonly associated with inflammatory and infectious bowel disease.

Selective endothelial binding of interleukin-2-dependent human T-cell lines derived from different tissues.

The ability of lymphocytes to recognize and bind to high endothelial venules (HEVs) is essential for lymphocyte migration from the blood into lymphoid tissues and into sites of inflammation. Endothelial cell binding capacity also critically determines the clinical usefulness of T-cell lines and clones in immunotherapy. In the present study, interleukin-2-dependent T-cell lines were derived from the blood, lamina propria of the gut, inflamed synovium, synovial fluid, and peripheral lymph nodes. After 3-8 weeks of culture, the expression of homing-associated molecules and binding to mucosal, synovial, and peripheral lymph node HEVs were analyzed. Cell lines derived from the blood and mucosal sites bound significantly better to mucosal and synovial HEVs than to peripheral lymph node HEVs. Three out of seven synovial T-cell lines showed preferential binding to synovial HEVs, whereas the rest bound almost equally well to synovial and mucosal HEVs. T-cell lines from peripheral lymph nodes bound preferentially to lymph node HEVs despite the lack of L-selectin (the peripheral lymph node homing receptor). Expression of the known homing-associated molecules did not predict the HEV-binding specificity of these lines. Importantly, two cell lines bound well to synovial venules, but poorly, if at all, to mucosal or peripheral lymph node HEVs, supporting the concept that synovial-specific HEV recognition mechanisms exist. In conclusion, the tissue origin of T-cell lines critically determines their selectivity for endothelial cell recognition, and besides the known "homing receptors," other molecules may also mediate tissue-specific HEV-binding of interleukin-2-activated T cells.

The hyaluronate receptor is a member of the CD44 (H-CAM) family of cell surface glycoproteins [published erratum appears in J Cell Biol 1991 Feb;112(3):following 513

The present study was undertaken to determine the relationship between the hyaluronate receptor and CD44 (H-CAM), cell-surface glycoproteins of similar molecular weights that have been implicated in cell adhesion. In initial experiments, a panel of monoclonal antibodies directed against CD44 were tested for their ability to cross react with the hyaluronate receptor. These antibodies immunoprecipitated [3H]hyaluronate binding activity from detergent extracts of both mouse and human cells, indicating that the hyaluronate receptor is identical to CD44. In addition, one of these antibodies (KM-201 to mouse CD44) directly blocked the binding of labeled hyaluronate to the receptor and inhibited hyaluronate dependent aggregation of SV-3T3 cells. CD44 has also been implicated in lymphocyte binding to high endothelial venules during lymphocyte homing. Interestingly, the monoclonal antibody Hermes-3, which blocks lymphocyte binding to the high endothelial venules of mucosal lymphoid tissue, had no effect on the binding of labeled hyaluronate. Furthermore, the binding of lymphocytes to high endothelial cells of lymph nodes and mucosal lymphoid tissue was not significantly affected by treatment with agents that block the binding of hyaluronate (hyaluronidase, excess hyaluronate and specific antibodies). Thus, CD44 appears to have at least two distinct functional domains, one for binding hyaluronate and another involved in interactions with mucosal high endothelial venules.

Monoclonal antibodies to human lymphocyte homing receptors define a novel class of adhesion molecules on diverse cell types.

A 90-kD lymphocyte surface glycoprotein, defined by monoclonal antibodies of the Hermes series, is involved in lymphocyte recognition of high endothelial venules (HEV). Lymphocyte gp90Hermes binds in a saturable, reversible fashion to the mucosal vascular addressin (MAd), a tissue-specific endothelial cell adhesion molecule for lymphocytes. We and others have recently shown that the Hermes antigen is identical to or includes CD44 (In[Lu]-related p80), human Pgp-1, and extracellular matrix receptor III-molecules reportedly expressed on diverse cell types. Here, we examine the relationship between lymphoid and nonlymphoid Hermes antigens using serologic, biochemical, and, most importantly, functional assays. Consistent with studies using mAbs to CD44 or Pgp-1, mAbs against five different epitopes on lymphocyte gp90Hermes reacted with a wide variety of nonhematolymphoid cells in diverse normal human tissues, including many types of epithelium, mesenchymal elements such as fibroblasts and smooth muscle, and a subset of glia in the central nervous system. To ask whether these non-lymphoid molecules might also be functionally homologous to lymphocyte homing receptors, we assessed their ability to interact with purified MAd using fluorescence energy transfer techniques. The Hermes antigen isolated from both glial cells and fibroblasts--which express a predominant 90-kD form similar in relative molecular mass, isoelectric point, and protease sensitivity to lymphocyte gp90Hermes--was able to bind purified MAd. In contrast, a 140-160-kD form of the Hermes antigen isolated from squamous epithelial cells lacked this capability. Like lymphocyte binding to mucosal HEV, the interaction between glial gp90Hermes and MAd is inhibited by mAb Hermes-3, but not Hermes-1, suggesting that similar molecular domains are involved in the two binding events. The observation that the Hermes/CD44 molecules derived from several nonlymphoid cell types display binding domains homologous to those of lymphocyte homing receptors suggests that these glycoproteins represent a novel type of cell adhesion/recognition molecule (H-CAM) potentially mediating cell-cell or cell-matrix interactions in multiple tissues.

A human lymphocyte homing receptor, the Hermes antigen, is related to cartilage proteoglycan core and link proteins

Lymphocyte interactions with high endothelial venules (HEV) during extravasation into lymphoid tissues involve an 85-95 kd class of lymphocyte surface glycoprotein(s), gp90Hermes (CD44). We report here the cloning of cDNA for gp90Hermes expressed in a mucosal HEV-binding B lymphoblastoid cell line, KCA. Northern hybridization revealed the presence of three invariant RNA bands at 1.5, 2.2, and 4.5 kb in mucosal HEV-, lymph node HEV-, or dual-binding cells. The deduced amino acid sequence predicts a mature protein with a C-terminal cytoplasmic tail, a hydrophobic transmembrane domain of 23 amino acids, and an N-terminal extracellular region of 248 amino acids. A proximal extracellular domain is the probable region of O-glycosylation and chondroitin sulfate linkage and displays at least two of the three immunodominant epitope clusters of native gp90Hermes. A distal region contains the majority of potential N-glycosylation sites and cysteines, and exhibits a striking homology to tandemly repeated domains of the cartilage link and proteoglycan core proteins. No significant similarities were found to the immunoglobulin, integrin, or cadherin gene families. Thus gp90Hermes represents a novel class of integral membrane protein involved in lymphocyte-endothelial cell interactions and lymphocyte homing.

The mucosal vascular addressin is a tissue-specific endothelial cell adhesion molecule for circulating lymphocytes.

Tissue position-dependent or address-dependent expression of cell adhesion molecules has been proposed to play a part in cellular positioning in a variety of systems, for example during neural development, the metastasis of neoplasms, and the tissue-specific homing of lymphocytes. The extravasation of blood-borne lymphocytes is regulated by interactions with the endothelium of specialised venules, such as the high endothelial venules (HEV) in organized lymph nodes and mucosal lymphoid tissues. At least three separate lymphocyte-HEV recognition systems have been described, one mediating tissue-selective lymphocyte interactions with HEV in peripheral lymph nodes, another in mucosal lymphoid organs, and a third in inflamed synovium. We have previously identified a tissue-specific 'vascular addressin' in the mouse which is selectively expressed by venules mediating lymphocyte-homing into mucosal tissues. To determine whether this addressin is a specific adhesion molecule for lymphocytes, we have isolated it by monoclonal antibody-affinity chromatography and inserted it into supported phospholipid planar membranes. Lymphocytes bind to membranes containing the addressin, but not to phospholipid bilayers or to control glycophorin-reconstituted membranes. Only those lymphocytes and lymphoma cell lines capable of binding to mucosal HEV adhere well to the isolated addressin; peripheral lymph node HEV-specific or HEV-non-binding cell lines do not bind. Binding is blocked by anti-addressin antibody MECA-367. We conclude that the mucosal vascular addressin is a tissue-specific endothelial cell-adhesion molecule for lymphocytes, and suggest that it could regulate lymphocyte traffic into mucosal tissues by mediating attachment of blood-borne cells to endothelium.

Human lamina propria lymphocytes bear homing receptors and bind selectively to mucosal lymphoid high endothelium

It has been hypothesized that the selective recognition of tissue-specific endothelial cell molecules helps determine the in vivo distribution of lymphoid effector cells by controlling the extravasation of their circulating precursors. Here we report (a) immunofluorescence studies of the cell surface phenotype of human lamina propria lymphocytes (LPL), including staining with monoclonal antibody Hermes-1, which defines a 90-kDa lymphocyte surface glycoprotein involved in recognition of high endothelial venules (HEV); and (b) functional analyses of the ability of LPL to bind to HEV in frozen sections of mucosal lymphoid tissues (appendix or Peyer's patch) vs. peripheral lymph nodes. Essentially all LPL bear the Hermes-1 antigen, over 90% at levels comparable to those of circulating PBL. As a population, LPL display a quantitative preference for adherence to mucosal HEV, binding 0.8-1.5 times as well as PBL to mucosal HEV, but only 0.1-0.5 times as well to HEV in peripheral lymph nodes. Of particular interest was the behavior of the lymphoblast fraction, which typically constituted 3-7% of LPL. These cells, defined by size, consisted of a mixture of T cells and surface IgA+ blasts. One hundred percent were Hermes-1 bright, and they bound 4-8 times more efficiently to mucosal HEV than PBL while failing to bind detectably to lymph node HEV. LPL binding to mucosal HEV involves the gp90 Hermes, since the monoclonal anti-gp90 antibody, Hermes-3, and a polyclonal anti-gp90 antiserum inhibit the binding of small LPL and of LP blasts. The remarkable efficiency and specificity of binding by LP blasts may reflect retention of homing properties of the blood-borne precursors of these blasts and is discussed in relation to the capacity of immunoblasts in mesenteric nodes and in thoracic duct lymph to traffic selectively to mucosal lymphoid and extralymphoid sites. The demonstration of organ-specific endothelial cell recognition by LP lymphoblasts provides considerable support for the concept that selective interactions with endothelium play an important role in directing the distribution of activated lymphocyte subsets in vivo.

Evolutionary conservation of tissue-specific lymphocyte-endothelial cell recognition mechanisms involved in lymphocyte homing.

Tissue-specific interactions with specialized high endothelial venules (HEV) direct the homing of lymphocytes from the blood into peripheral lymph nodes, mucosal lymphoid organs, and tissue sites of chronic inflammation. These interactions have been demonstrated in all mammalian species examined and thus appear highly conserved. To assess the degree of evolutionary divergence in lymphocyte-HEV recognition mechanisms, we have studied the ability of lymphocytes to interact with HEV across species barriers. By using an in vitro assay of lymphocyte binding to HEV in frozen sections of lymphoid tissues, we confirm that mouse, guinea pig, and human lymphocytes bind to xenogeneic as well as homologous HEV. In addition, we show that mouse and human lymphoid cell lines that bind selectively to either peripheral lymph node or mucosal vessels (Peyer's patches, appendix) in homologous lymphoid tissues exhibit the same organ specificity in binding to xenogeneic HEV. Furthermore, monoclonal antibodies that recognize lymphocyte "homing receptors" and block homologous lymphocyte binding to peripheral lymph node or to mucosal HEV, also inhibit lymphocyte interactions with xenogeneic HEV in a tissue-specific fashion. Similarly, anti-HEV antibodies against organ-specific mouse high endothelial cell "addressins" involved in lymphocyte homing to peripheral lymph node or mucosal lymphoid organs, not only block the adhesion of mouse lymphocytes but also of human lymphocytes to target mouse HEV. The results illustrate a remarkable degree of functional conservation of elements mediating these cell-cell recognition events involved in organ-specific lymphocyte homing.

Lymphocyte recognition of high endothelium: antibodies to distinct epitopes of an 85-95-kD glycoprotein antigen differentially inhibit lymphocyte binding to lymph node, mucosal, or synovial endothelial cells.

The tissue-specific homing of lymphocytes is directed by specialized high endothelial venules (HEV). At least three functionally independent lymphocyte/HEV recognition systems exist, controlling the extravasation of circulating lymphocytes into peripheral lymph nodes, mucosal lymphoid tissues (Peyer's patches or appendix), and the synovium of inflamed joints. We report here that antibodies capable of inhibiting human lymphocyte binding to one or more HEV types recognize a common 85-95-kD lymphocyte surface glycoprotein antigen, defined by the non-blocking monoclonal antibody, Hermes-1. We demonstrate that MEL-14, a monoclonal antibody against putative lymph node "homing receptors" in the mouse, functionally inhibits human lymphocyte binding to lymph node HEV but not to mucosal or synovial HEV, and cross-reacts with the 85-95-kD Hermes-1 antigen. Furthermore, we show that Hermes-3, a novel antibody produced by immunization with Hermes-1 antigen isolated from a mucosal HEV-specific cell line, selectively blocks lymphocyte binding to mucosal HEV. Such tissue specificity of inhibition suggests that MEL-14 and Hermes-3 block the function of specific lymphocyte recognition elements for lymph node and mucosal HEV, respectively. Recognition of synovial HEV also involves the 85-95-kD Hermes-1 antigen, in that a polyclonal antiserum produced against the isolated antigen blocks all three classes of lymphocyte-HEV interaction. From these studies, it is likely that the Hermes-1-defined 85-95-kD glycoprotein class either comprises a family of related but functionally independent receptors for HEV, or associates both physically and functionally with such receptors. The findings imply that related molecular mechanisms are involved in several functionally independent cell-cell recognition events that direct lymphocyte traffic.