The skin-associated chemokine CCL27 (also called CTACK, ALP and ESkine) and its receptor CCR10 (GPR-2) mediate chemotactic responses of skin-homing T cells in vitro. Here we report that most skin-infiltrating lymphocytes in patients suffering from psoriasis, atopic or allergic-contact dermatitis express CCR10. Epidermal basal keratinocytes produced CCL27 protein that bound to extracellular matrix, mediated adhesion and was displayed on the surface of dermal endothelial cells. Tumor necrosis factor-alpha and interleukin-1beta induced CCL27 production whereas the glucocorticosteroid clobetasol propionate suppressed it. Circulating skin-homing CLA+ T cells, dermal microvascular endothelial cells and fibroblasts expressed CCR10 on their cell surface. In vivo, intracutaneous CCL27 injection attracted lymphocytes and, conversely, neutralization of CCL27-CCR10 interactions impaired lymphocyte recruitment to the skin leading to the suppression of allergen-induced skin inflammation. Together, these findings indicate that CCL27-CCR10 interactions have a pivotal role in T cell-mediated skin inflammation.

The lectin homing receptor LECAM-1 (LAM-1, Leu8) and the P2 integrins, particularly Mac-i (CD11b/CD18), participate in leukocyte-endothelial cell interactions in inflammation. LECAM-1 is rapidly shed whileMac-i expression is dramatically increased upon neutrophil activation, suggesting functionally distinct roles for these molecules. Using intravital video microscopy, we have compared the effect of antibodies against LECAM-1 and CD18 on leukocyte interactions with rabbit mesenteric venules. Anti-LECAM-i monoclonal antibody and its Fab fragments inhibited initial reversible leukocyte rolling along the vascular wall.Anti-CD18 monoclonal antibody had no effect on rolling but prevented subsequent firm attachment of leukocytes to venular endothelium. Antibodies to CD18, the leukocyte integrin P2 chain, block firm attachment and diapedesis of neutrophils but have no effect on leukocyte rolling at normal venular shear rates (1). The surface molecules on leukocytes and endothelial cells that mediate rolling have not been defined. Rolling is attenuated by superoxide dismutase and action of oxygen-derived free radicals on endothelial cells may play a role in its induction (2,3). This unique event is calcium dependent (4) and can be inhibited by intravenous injection of neuraminidase but not sialic acid (5) and by some (but not all) polyanionic polysaccharides, such as dextran sulfate or heparin (6-9). These findings suggest a possible role for cell-surface adhesion receptors with affinity for charged carbohydrates.The leukocyte surface selectin/LEC-CAM LECAM-1 (LAM-1, Leu8), the peripheral lymph node homing receptor (10, 11), has been implicated in leukocyte interactions with activated endothelium in inflammation. The lectin domain in the extracellular portion of LECAM-1 contains many positively charged amino acids (12)(13)(14) and can interact with certain anionic carbohydrates (15). Anti-LECAM-1 monoclonal antibodies (mAbs) block neutrophil binding to cytokine-activated endothelial cells in vitro, inhibiting an adhesion pathway that is independent of (2 integrin function (16, 17). Administration of anti-LECAM-1 mAbs or a soluble homing receptor-IgG chimeric molecule as well as removal of LECAM-1 from the cell surface dramatically reduces leukocyte extravasation into sites of acute inflammation in various inflammatory models (18-21). The finding that LECAM-1 is rapidly shed from the neutrophil surface in response to several cytokines in vivo (20, 21) and in vitro (22, 23) in conjunction with observations of a parallel increase in (2 integrin expression has led to the hypothesis that LECAM-1 might mediate early neutrophil adhesive events, preceding the role of activation-triggered (32 integrins (20)(21)(22)(23). Such early events might be involved in leukocyte rolling. The present studies were undertaken to examine the role of LECAM-1 in in situ leukocyte interactions with venular endothelium in the rabbit mesentery.MATERIALS AND METHODS Antibodies. mAb DREG-200, which reacts with a surface molecule on rabbit...

In contrast to naive lymphocytes, memory͞effector lymphocytes can access nonlymphoid effector sites and display restricted, often tissue-selective, migration behavior. The cutaneous lymphocyteassociated antigen (CLA) defines a subset of circulating memory T cells that selectively localize in cutaneous sites mediated in part by the interaction of CLA with its vascular ligand E-selectin. Here, we report the identification and characterization of a CC chemokine, cutaneous T cell-attracting chemokine (CTACK). Both human and mouse CTACK are detected only in skin by Southern and Northern blot analyses. Specifically, CTACK message is found in the mouse epidermis and in human keratinocytes, and anti-CTACK mAbs predominantly stain the epithelium. Finally, CTACK selectively attracts CLA ؉ memory T cells. Taken together, these results suggest an important role for CTACK in recruitment of CLA ؉ T cells to cutaneous sites. CTACK is predominantly expressed in the skin and selectively attracts a tissue-specific subpopulation of memory lymphocytes.

The L-selectin, a cell surface C-type lectin, directs lymphocyte traffic to lymph nodes, and contributes to lymphocyte homing to Peyer's patches and to leukocyte interactions with inflamed venules. Here we report that the mucosal vascular addressin MAdCAM-1, a mucosal endothelial adhesion molecule with immunoglobulin- and mucin-like domains, is a facultative ligand for L-selectin. MAdCAM-1 isolated from mesenteric lymph nodes, but not from cultured endothelioma cells, bears N-glycanase-resistant sialic acid-containing carbohydrate which supports adhesion of L-selectin-transfected lymphoid cells under shear. Interacting lymphoid cells display a 'rolling' behaviour similar to the selectin-dependent rolling of neutrophils observed in inflamed venules. MAdCAM-1 is also a ligand for the lymphocyte integrin homing receptor for Peyer's patches, alpha 4 beta 7 (ref. 7), and may be uniquely adapted to support both selectin-mediated lymphocyte rolling and integrin-mediated adhesion and arrest in vivo.

Mice without secreted TNF but with functional, normally regulated and expressed membrane-bound TNF (memTNF(Delta/Delta) mice) were created by knocking-in the uncleavable Delta 1-9,K11E TNF allele. In contrast to TNF-deficient mice (TNF(-/-)), memTNF supported many features of lymphoid organ structure, except generation of primary B cell follicles. Splenic chemokine expression was near normal. MemTNF-induced apoptosis was mediated through both TNF-R1 and TNF-R2. That memTNF is suboptimal for development of inflammation was revealed in experimental autoimmune encephalomyelitis. Disease severity was reduced in memTNF(Delta/Delta) mice relative to wild-type mice, and the nature of spinal cord infiltrates resembled that in TNF(-/-) mice. We conclude that memTNF supports many processes underlying lymphoid tissue structure, but secreted TNF is needed for optimal inflammatory lesion development.

Chemokines have been hypothesized to contribute to the selectivity of lymphocyte trafficking not only as chemoattractants, but also by triggering integrin-dependent sticking (arrest) of circulating lymphocytes at venular sites of extravasation. We show that T cells roll on most Peyer's patch high endothelial venules (PP-HEVs), but preferentially arrest in segments displaying high levels of luminal secondary lymphoid tissue chemokine (SLC) (6Ckine, Exodus-2, thymus-derived chemotactic agent 4 [TCA-4]). This arrest is selectively inhibited by functional deletion (desensitization) of CC chemokine receptor 7 (CCR7), the receptor for SLC and for macrophage inflammatory protein (MIP)-3β (EBV-induced molecule 1 ligand chemokine [ELC]), and does not occur in mutant DDD/1 mice that are deficient in these CCR7 ligands. In contrast, pertussis toxin–sensitive B cell sticking does not require SLC or MIP-3β signaling, and occurs efficiently in SLClow/− HEV segments in wild-type mice, and in the SLC-negative HEVs of DDD/1 mice. Remarkably, sites of T and B cell firm adhesion are segregated in PPs, with HEVs supporting B cell accumulation concentrated in or near follicles, the target domain of most B cells entering PPs, whereas T cells preferentially accumulate in interfollicular HEVs. Our findings reveal a fundamental difference in signaling requirements for PP-HEV recognition by T and B cells, and describe an unexpected level of specialization of HEVs that may allow differential, segmental control of lymphocyte subset recruitment into functionally distinct lymphoid microenvironments in vivo.

Hypercholesterolemia enhances the adhesiveness of aortic endothelium for monocytes; this effect is attenuated by dietary L-arginine. Conversely, inhibition of NO synthesis enhances monocyte binding. The results suggest that endothelium-derived NO plays an important role in regulating the endothelial adhesiveness for monocytes. Alterations in NO activity may play a critical role in atherogenesis.

Tissue-specific homing of lymphocytes is regulated by interactions with the endothelium of specialized venules, such as the high endothelial venules (HEV) in lymph nodes and mucosal lymphoid tissues. The mucosal vascular addressin, a 58-66K glycoprotein adhesion receptor for lymphocytes, is selectively expressed on HEV of mucosal lymphoid organ and on lamina propria venules and helps direct lymphocyte traffic to these mucosal tissues. We now report the isolation of a complementary DNA that, on transfection into COS cells, encodes immunoreactive addressin that specifically binds the mucosal HEV-binding T-cell lymphoma TK1. The predicted amino-acid sequence defines the mucosal addressin as a novel immunoglobulin family member, MAdCAM-1, with two amino-terminal domains that display strong homology to previously described vascular adhesion receptors for leukocytes, ICAM-1 (ref. 6) and VCAM-1 (ref. 7). The membrane proximal domain is homologous to the third domain (C alpha 2) of another mucosa-associated immunoglobulin family member, IgA1 (refs 8, 9). In addition to the immunoglobulin domains, there is a serine/threonine-rich region which may serve as a backbone to present carbohydrate ligands to lymphocytes. MAdCAM-1 is thus a complex multidomain receptor displaying several structural motifs that may participate in lymphocyte homing interactions.