Cutaneous lymphocyte-associated antigen (CLA) T cells up-regulate P-selectin ligand expression upon their activation

Memory T cells expressing CLA occur in humans and accumulate in normal and inflamed skin. These cells uniformly bind to the vascular adhesion molecule E-selectin, yet only a subset binds to P-selectin. The latter cells are distinguished by the mAb CHO-131, and are enriched in psoriasis lesions. Activated T cells up-regulate CLA expression, but little is currently known about their binding to P-selectin. We observed that CLA⁺ CD4⁺ T cells derived from stimulated naive T cells uniformly express the CHO-131 epitope. This occurred as well upon the restimulation of memory CLA⁺ CD4⁺ T cells. The latter cells also expressed higher levels of PSGL-1 modified by P-selectin glycan ligands; C2GlcNAcT-1 mRNA, a glycosyltransferase critical for such glycan synthesis; and more uniformly bound to P-selectin. Our findings thus indicate that unlike memory CLA⁺ CD4⁺ T cells, when activated these cells can broadly bind to P-selectin, suggesting a more diverse tissue trafficking capacity.     

Translational Mini‐Review Series on Immunology of Vascular Disease: Accelerated atherosclerosis in vasculitis

The cutaneous leucocyte‐associated antigen receptor (CLA) can direct Leishmania‐specific T lymphocytes towards inflamed skin lesions. Homing receptors [CLA, lymphocyte‐associated antigen 1 (LFA‐1) or CD62L] were analysed in lymphocytes from blood and cutaneous leishmaniasis (CL) lesions. CL patients with active lesions (A‐CL) presented lower levels of T lymphocytes expressing the CLA⁺ phenotype (T CD4⁺ = 10·4% ± 7·5% and T CD8⁺ = 5·8% ± 3·4%) than did healthy subjects (HS) (T CD4⁺ = 19·3% ± 13·1% and T CD8⁺ = 21·6% ± 8·8%), notably in T CD8⁺ (P < 0·001). In clinically cured patients these percentages returned to levels observed in HS. Leishmanial antigens up‐regulated CLA in T cells (CLA⁺ in T CD4⁺ = 33·3% ± 14·1%; CLA⁺ in T CD8⁺ = 22·4% ± 9·4%) from A‐CL but not from HS. An enrichment of CLA⁺ cells was observed in lesions (CLA⁺ in T CD4⁺ = 45·9% ± 22·5%; CLA⁺ in T CD8⁺ = 46·4% ± 16·1%) in comparison with blood (CLA⁺ in T CD4⁺ = 10·4% ± 7·5%; CLA⁺ in T CD8⁺ = 5·8% ± 3·4%). Conversely, LFA‐1 was highly expressed in CD8⁺ T cells and augmented in CD4⁺ T from peripheral blood of A‐CL patients. In contrast, CD62L was not affected. These results suggest that Leishmania antigens can modulate molecules responsible for migration to skin lesions, potentially influencing the cell composition of inflammatory infiltrate of leishmaniasis or even the severity of the disease.     

Expression of the chemokine receptors CCR4, CCR5, and CXCR3 by human tissue-infiltrating lymphocytes.

Differential expression of adhesion molecules and chemokine receptors has been useful for identification of peripheral blood memory lymphocyte subsets with distinct tissue and microenvironmental tropisms. Expression of CCR4 by circulating memory CD4(+) lymphocytes is associated with cutaneous and other systemic populations while expression of CCR9 is associated with a small intestine-homing subset. CCR5 and CXCR3 are also expressed by discrete memory CD4(+) populations in blood, as well as by tissue-infiltrating lymphocytes from a number of sites. To characterize the similarities and differences among tissue-infiltrating lymphocytes, and to shed light on the specialization of lymphocyte subsets that mediate inflammation and immune surveillance in particular tissues, we have examined the expression of CCR4, CXCR3, and CCR5 on CD4(+) lymphocytes directly isolated from a wide variety of normal and inflamed tissues. Extra-lymphoid tissues contained only memory lymphocytes, many of which were activated (CD69(+)). As predicted by classical studies, skin lymphocytes were enriched in CLA expression whereas intestinal lymphocytes were enriched in alpha(4)beta(7) expression. CCR4 was expressed at high levels by skin-infiltrating lymphocytes, at lower levels by lung and synovial fluid lymphocytes, but never by intestinal lymphocytes. Only the high CCR4 levels characteristic of skin lymphocytes were associated with robust chemotactic and adhesive responses to TARC, consistent with a selective role for CCR4 in skin lymphocyte homing. In contrast, CXCR3 and CCR5 were present on the majority of lymphocytes from each non-lymphoid tissue examined, suggesting that these receptors are unlikely to determine tissue specificity, but rather, may play a wider role in tissue inflammation.     

B and T lymphocyte subsets enter peripheral lymph nodes and Peyer's patches without preference in vivo: no correlation occurs between their localization in different types of high endothelial venules and the expression of CD44, VLA-4, LFA-1, ICAM-1, CD2 or L-selectin

Many lymphocytes enter tissues such as peripheral lymph nodes and Peyer's patches through high endothelial venules (HEV). It is known that HEV differ in the expression of adhesion molecules as lymphocyte subsets do. Through the interaction of these molecules B and T lymphocyte subsets are thought to be preferentially directed into lymphoid organs. However, it is unclear which role these mechanisms play in vivo, since there are no studies demonstrating that blood lymphocyte subsets preferentially interact with different types of HEV in vivo. Therefore, in the present study the frequency of B, T, CD4⁺ and CD8⁺ lymphocytes in the wall of the HEV of rat peripheral lymph nodes and Peyer's patches was analyzed by immunohistology. In addition, the expression of CD44, VLA-4, LFA-1, ICAM-1, CD2 and L-selectin on B and T lymphocyte subsets of the blood was determined by flow cytometry. Although B and T lymphocytes showed significantly different levels of expression for each adhesion molecule investigated, the relation of B and T lymphocytes within the HEV of peripheral lymph nodes and Peyer's patches was strikingly comparable (38.0 ± 5.2% vs. 40.6 ± 5.7% and 62.0 ± 5.2% vs. 59.4 ± 5.7%, respectively). The same was true for CD4⁺ and CD8⁺ cells. Thus, although HEV and the blood lymphocyte subsets differ markedly in their expression pattern of adhesion molecules, the existing levels are sufficient to mediate comparable entrance of B and T lymphocyte subsets into both types of HEV.     

Lymphocyte binding to vascular endothelium in inflamed skin revisited: a central role for vascular adhesion protein-1 (VAP-1)

The binding of leukocytes to vascular endothelium and their migration into tissues is mediated by adhesion molecules on the endothelial cells and leukocytes. Vascular adhesion protein-1 (VAP-1) is a 170–180/90-kDa endothelial molecule expressed most prominently in high endothelial venules in peripheral lymph node (PLN) type lymphatic tissues. VAP-1 mediates lymphocyte binding to PLN, tonsil and synovium. The expression of VAP-1 is induced in inflammatory diseases such as arthritis and gut inflammation. We examined the expression, structure and function of VAP-1 in normal and inflamed skin and compared it to those of other adhesion molecules implicated in skin homing. In psoriasis, lichen ruber planus, pemphigoid and allergic lesions, VAP-1 was markedly up-regulated. The expression of VAP-1 was also increased in biopsies of healthy skin of the patients. The VAP-1 molecule induced in skin is decorated with abundant sialic acids. VAP-1 in inflamed skin is functional, since inhibition with anti-VAP-1 monoclonal antibodies caused a 60% reduction in lymphocyte adhesion to vascular endothelium. Antibodies against E-selectin, which has been regarded as the major vascular addressin directing cutaneous lymphocyte traffic, and, surprisingly, against peripheral lymph node addressin (PNAd), caused inhibitions of 30% and 60%, respectively, in the frozen section adhesion assay. These findings suggest important roles also for VAP-1 and PNAd in lymphocyte homing into inflamed skin.     

Phenotypic and functional analysis of CD4+ NKRP1A+ human T lymphocytes. Direct evidence that the NKRP1A molecule is involved in transendothelial migration

In this report, we show that among human CD4⁺ T lymphocytes 5–20% express the C-type lectin molecule NKRP1A. This lymphocyte subset displays a slightly more limited T cell receptor Vβ repertoire than the CD4⁺ NKRP1A^? counterpart. CD4⁺ NKRP1A⁺ T lymphocytes are characterized by a high expression of β1 and β2 integrins, thus representing a T lymphocyte subset that can possibly adhere and migrate through vascular endothelium. Indeed, resting CD4⁺ NKRP1A⁺ lymphocytes, differently from the CD4⁺ NKRP1A^? subset, migrated across endothelial cell monolayers in a Transwell chamber system. Pre-treatment of CD4⁺ NKRP1A⁺ T lymphocytes with an anti-NKRP1A monoclonal antibody (mAb) strongly reduced transendothelial migration, suggesting the involvement of the NKRP1A molecule in the transmigration process. Furthermore, cells of the NKRP1A^? Jurkat CD4⁺ T cell line stably transfected with NKRP1A cDNA migrated more rapidly and efficiently than either untransfected or mock-transfected Jurkat cells. Finally, mAb-mediated cross-linking of NKRP1A molecules in CD4⁺ T lymphocytes induced the up-regulation of the lymphocyte function-associated antigen 1 Mg²⁺-binding site as well as β1 and β2 integrin chains. Altogether, these findings suggest that the NKRP1A molecule is involved in transendothelial migration of resting CD4⁺ T lymphocytes.     

Peripheral Blood Lymphocyte Adhesion Molecule Deployment in the Immune Response

Using precise and reproducible flow cytometric measurements, the surface densities of the cell adhesion molecules (CAMs) CD29, CD2 and CD11a were studied on the CAMhigh (primed) subsets of peripheral blood CD4⁺ and CD8⁺ lymphocytes in 56 healthy subjects; 18 patients with acute bacterial infections, 19 with acute viral infections and 18 with chronic inflammatory conditions. By Mann–Whitney analysis, with significant P values adjusted for multiple comparisons to <0.0007, patients with viral infections were found to have increased CD11a on CAMhigh cells (an increase in median values of 13.7% for CD4⁺ lymphocytes and 15.8% for CD8⁺ lymphocytes); patients with chronic conditions have increased CD29 on CD8⁺CAMhigh lymphocytes (an increase in the median of 19%); and patients with bacterial infections have increased CD2 on CD8⁺CAMhigh cells (an increase in the median of 8%). There were marked individual increases in CD29 density: eight (15%) patients had CD29 gender-adjusted density on CD4⁺ cells greater than the control mean + 3 standard deviations (SD). CD29 densities on CD8⁺ cells were elevated to > control mean + 3 SD in 12 (22%) patients. By multiple regression analysis CD11a density on CD8⁺ and CD4⁺ cells and CD2 density on CD4⁺ cells were found to be associated with HLA-DR expression, but not with CD25 expression. Using standardized intercepts the authors demonstrated that there are very few circulating CD11ahighCD25⁺ cells, suggesting that these are rapidly extravasated. This study demonstrates that in disease, lymphocyte adhesion molecules are not deployed in concert and there are characteristic deployment patterns for different types of immune response.     

L-selectin in patients with common variable immunodeficiency (CVID): a comparative study with normal individuals

L-selectin is one of the key members of the selectin family of adhesion molecules and initiates leucocyte attachment to specialized high endothelial venules. The shed form, which retains functional activity, can be detected in biological fluids and is increased in diseases of many kinds. In the present study, we investigated L-selectin expression on leucocytes and measured the soluble form in the plasma of healthy individuals and patients with CVID. A significant loss of L-selectin expression is found on CVID B cells, which is marked by the presence of a substantial population of L-selectin-negative B cells in the peripheral blood of some CVID patients. On CD4⁺ T cells, the loss in L-selectin expression affects mostly the CD45RO⁺ population. Peripheral blood leucocytes other than lymphocytes express L-selectin molecule normally. Moreover, soluble L-selectin was detected in significantly increased levels in CVID plasma compared with healthy controls. Our data suggest that the loss of L-selectin expressed by lymphocytes may be due to increased or aberrant lymphocyte activation in CVID patients who remain immunodeficient, and down-regulation of L-selectin from these lymphocytes may significantly contribute to the elevated levels of soluble L-selectin in the plasma, which may in turn affect further lymphocyte trafficking.     

Activation of CD44 induces ICAM-1/LFA-1-independent,Ca2+, Mg2+, —independent adhesion pathway in lymphocyte-endothelial cell interaction

We have established an endothelial cell line KOP2.16 from pooled mouse lymph nodes. Resting lymphocytes avidly bound to KOP2.16 and migrated underneath the cytoplasm. The binding was partly mediated by VLA-4 and VCAM-1, but apparently independent of CD44 since anti-CD44 antibody examined failed to inhibit the binding. However, pretreatment of lymphocytes with anti-CD44 resulted in the rapid appearance of Ca²⁺-, Mg²⁺-independent, LFA-1/ICAM-1-, CD2/LFA-3,VLA-4/VCAM-l-independent lymphocyte binding, indicating that a novel adhesion pathway was induced by the anti-CD44 treatment. Interestingly, the elicited adhesion was observed only when anti-CD44 that block hyaluronate recognition of CD44 were used for lymphocyte pretreatment. Neither hyaluronate itself nor non-blocking anti-CD44 up-regulated the adhesion. Fab fragment of the blocking anti-CD44 did not induce the up-regulation unless cross-linked with a second antibody, indicating that cross-linking of surface CD44 is necessary for induction of a novel adhesion pathway. We propose that the agonistic anti-CD44 antibodies induce a novel adhesion pathway by mimicking ligand binding to CD44 on the lymphocyte surface and that non-hyaluronate ligand(s) is involved in regulation of adhesive function of CD44. Potential involvement of such a regulatory mechanism in lymphocyte homing is discussed.     

Potential role of the chemokine receptors CXCR3, CCR4, and the integrin alphaEbeta7 in the pathogenesis of psoriasis vulgaris

Various adhesion molecules have been implicated in T lymphocyte binding to dermal vascular endothelium in psoriasis vulgaris, but the chemotactic signals that promote subsequent homing into the adjacent dermis and overlying epidermis are poorly defined. We studied chemokine receptor (CCR1-CCR5, CXCR1-CXCR3), chemokine (interferon-gamma inducible protein 10 [IP-10]), monokine induced by interferon-gamma (MIG), thymus and activation-regulated chemokine (TARC), macrophage-derived chemokine (MDC), and adhesion molecule (cutaneous lymphocyte antigen [CLA], E-selectin, lymphocyte function-associated antigen-1 [LFA-1], intercellular adhesion molecule-1 [ICAM-1], very late antigen 4 [VLA-4], vascular cell adhesion molecule-1 [VCAM-1], alphaEbeta7, and E-cadherin) expression in psoriasis by immunohistology, flow cytometry, and molecular techniques. CXCR3 and CCR4 were expressed by dermal CD3+ lymphocytes, and their chemokine ligands, IP-10, MIG, TARC, and MDC, were up-regulated in psoriatic lesions. Keratinocytes stimulated with tumor necrosis factor-alpha and interferon-gamma up-regulated expression of IP-10, MIG, and MDC mRNA, whereas dermal endothelial cells, similarly stimulated, up-regulated expression of IP-10, MDC, and TARC mRNA, suggesting that these cell types were sources of the chemokines detected in biopsies. There was enhanced expression of E-selectin, CLA, LFA-1, ICAM-1, VLA-4, VCAM-1, and alphaEbeta7 in psoriatic lesions versus nonlesional skin. Finally, intra-epidermal CLA+ and alphaEbeta7+ T lymphocytes selectively expressed the chemokine receptor CXCR3. Collectively, these data suggest that CXCR3 and CCR4 may be involved in T lymphocyte trafficking to the psoriatic dermis and that CXCR3 is selectively involved in subsequent T cell homing to the overlying epidermis.     

Peripheral Blood T-Cell Responses to Keratin Peptides that Share Sequences with M Proteins are Largely Restricted to Skin-Homing CD8+ T Cells

The association of psoriasis with throat infections by streptococcus pyogenes suggests a potential antigenic target for the T cells that are known to infiltrate dermis and epidermis of psoriatic skin. Streptococcal M protein shares an extensive sequence homology with human epidermal keratins. Keratins 16 (K16) and 17 (K17) are mostly absent from uninvolved skin but are upregulated in psoriatic lesions. There is increasing evidence that CD8⁺ T cells play an important effector role in psoriasis and M protein‐primed T cells may recognize these shared epitopes in skin via molecular mimicry. To identify candidate epitopes, peptides with sequences from K17 were selected on the basis of predicted binding to HLA‐Cw6 and sequence similarities with M6 protein. Matched peptides from the sequence of M6 protein and a set of peptides with poor predicted binding were also selected. Cw6⁺ individuals with psoriasis and Cw6⁺ healthy controls, having a family history of psoriasis, were recruited. PBMCs were incubated with the peptide antigens. T‐cell activation in the CD4⁺, CD8⁺ and later the skin‐homing cutaneous lymphocyte‐associated antigen (CLA)‐expressing subset of CD8⁺ T cells was evaluated by CD69 expression and intracellular IFN‐γ accumulation using flow cytometry. We demonstrate that Cw6⁺ psoriasis patients had significant CD8⁺ T‐cell IFN‐γ responses to peptides from K17 and M6 protein selected on the basis of sequence homology and predicted HLA‐Cw*0602 binding. These responses were about 10 times more frequent in the skin‐homing cutaneous lymphocyte‐associated antigen‐expressing (CLA⁺) subset of CD8⁺ T cells. CD4⁺ T cells showed only borderline responses. CD8⁺ T cells from Cw6 + nonpsoriatic individuals responded to some M6 peptides but very rarely to K17 peptides, and this also applied to the CLA⁺CD8⁺ subset. These findings indicate that psoriatic individuals have CD8⁺ T cells that recognize keratin self‐antigens and that epitopes shared by streptococcal M protein and human keratin may be targets for the CD8⁺ T cells that infiltrate psoriatic skin lesions.     

CD40 is functionally expressed on human keratinocytes

The CD40/gp39 pathway is known to be an important feature of B/T cell collaboration leading to T cell-dependent activation, proliferation or differentiation of B cells. Additionally, CD40 is involved in the regulation of B cell survival and apoptosis. Recently, CD40 has been shown to be expressed functionally on non-hematopoietic cells, i.e. endothelial cells. Here, we demonstrate that human keratinocytes (KC) cultured in vitro express CD40 constitutively. The surface expression of CD40 is markedly up-regulated following stimulation with interferon (IFN)-γ, but not with tumor necrosis factor-α or interleukin (IL)-1β. This process is regulated at the CD40 mRNA level as demonstrated by Northern blot analysis. Furthermore, ligation of CD40 via soluble gp39, the CD40 ligand, enhances intercellular adhesion molecule (ICAM)-1 and Bcl-x up-regulation on IFN-γ-stimulated KC, but not lymphocyte function-associated antigen (LFA)-3, B7-2, HLA-DR, or Fas expression. The release of IL-8 is also induced following CD40 ligation on KC. In psoriasis, a T cell-mediated inflammatory skin disease, KC have a markedly enhanced expression of CD40. This expression co-localizes with the expression of ICAM-1, Bcl-x, and an influx of CD3⁺ T cells. These findings suggest a functional role of CD40 on KC in inflammatory skin disorders such as psoriasis and could make a therapeutic intervention by disrupting the CD40/gp39 pathway an approach to consider in these inflammatory skin diseases.     

IL-6 acts on endothelial cells to preferentially increase their adherence for lymphocytes

Using a quantitative monolayer adhesion assay, the current report shows that treatment of human umbilical vein endothelial cells (HUVEC) with IL-6 increases their adhesiveness for blood lymphocytes, particularly CD4⁺ cells, but not for polymorphonuclear cells and monocytes. This effect, which was most pronounced when using low concentrations of the cytokine (0.1–1.0 U/ml) and a short incubation period (4 h), was also apparent with microvascular endothelial cells and a hybrid endothelial cell line. Skin lesions from patients with mycosis fungoides contain high levels of IL-6, and blood lymphocytes from patients with this disorder also exhibited an enhanced adhesion to IL-6-treated HUVEC. The cytokine enhanced intercellular adhesion molecule-1 (ICAM-1) expression and induced the expression of vascular cell adhesion molecule-1 (VCAM-1) and E-selectin on endothelial cells. Antibody blocking studies demonstrated that the vascular adhesion molecules ICAM-1, VCAM-1 and E-selectin and the leucocyte integrin LFA-1 all contributed to lymphocyte binding to endothelium activated by IL-6. It is proposed that IL-6 may be involved in the recruitment of lymphocytes into non-lymphoid tissue.     

Lymphocyte migration to inflamed lacrimal glands is mediated by vascular cell adhesion molecule-1/alpha(4)beta(1) integrin, peripheral node addressin/l-selectin, and lymphocyte function-associated antigen-1 adhesion pathways

Sjogren's syndrome is an autoimmune disease characterized by inflammation and destruction of lacrimal and salivary glands. The development of the inflammation requires the migration of lymphocytes from the blood into these tissues. This migration involves multistep cascades with binding of lacrimal gland endothelial adhesion molecules to their ligands on circulating lymphocytes. We used nonobese diabetic mice, which develop autoimmune-mediated lacrimal gland inflammation, as an experimental model to define the adhesion molecules that control lymphocyte migration into inflamed lacrimal glands. We found that vascular endothelia in inflamed areas of lacrimal gland expressed vascular cell adhesion molecule (VCAM)-1 and the peripheral node addressin (PNAd), but not mucosal addressin cell adhesion molecule-1. Most lymphocytes in the inflamed glands expressed alpha(4) integrin, L-selectin, and lymphocyte function-associated antigen (LFA)-1. In vivo studies revealed that antibodies against VCAM-1, alpha(4) integrin, PNAd, L-selectin, or LFA-1 almost completely blocked lymphocyte migration from blood into inflamed lacrimal glands. There was no inhibition of migration by antibodies against mucosal addressin cell adhesion molecule-1 or alpha(4)beta(7) integrin. These results indicate that endothelial/lymphocyte adhesion cascades involving VCAM-1/alpha(4)beta(1) integrin, PNAd/L-selectin, and LFA-1 control the migration of lymphocytes into inflamed lacrimal gland. These adhesion molecules offer potential therapeutic targets to block the development of lacrimal gland inflammation and destruction.     

Conjugated linoleic acids alleviated immunosuppression in broiler chickens exposed to cyclosporin A

An experiment with 3×2 factorial arrangement was carried out to determine the effects of dietary conjugated linoleic acids (CLA) on immune function in cyclosporin A (CsA)-immunosuppressed chickens. Two hundred and sixteen one-day-old chickens were randomly allocated into six treatments with CLA (80:20 of c9, t11-CLA:t10, c12-CLA) levels (0, 1.0% and 2.0%) and immunosuppression (treated with CsA or saline with olive oil). CsA treatment significantly (P<0.05) decreased peripheral blood lymphocyte proliferation in response to concanavalin A (Con A) mitogen, CD4⁺ lymphocyte subsets and Interleukin-2 (IL-2) production. CLA diets significantly (P<0.05) increased the relative weight of the bursa, lymphocyte proliferation in response to Con A, IL-2 production and CD4⁺ lymphocyte subsets. Interaction between CLA and CsA on lymphocyte proliferation in response to Con A and CD4⁺ lymphocyte subsets was observed, which indicated that c9, t11-CLA may play a primary role in enhancing immune function under both normal physiological and immunosuppressive conditions.     

Functional evidence that the HECA-452 antigen is involved in the adhesion of human neutrophils and lymphocytes to tumour necrosis factor-alpha-stimulated endothelial cells.

The migration of leucocytes into tissues is a process mediated by leucocyte endothelial interactions, in which adhesion receptors play a crucial role. Recently, it was found that 80-90% of T cells in inflammatory skin diseases were reactive to the monoclonal antibody (mAb) HECA-452+ in contrast to inflamed non-cutaneous tissues. It was suggested that the HECA-452 antigen is a homing receptor for lymphocyte migration into skin. This receptor was designated cutaneous lymphocyte-associated antigen or CLA and subsequently identified as a group of related sugar moieties. E-selectin, formerly known as ELAM-1 expressed by the endothelium has been implicated to be a counter-receptor for CLA. In this study, we investigated the adhesion of HECA-452+ leucocytes, i.e. freshly isolated neutrophils and B-cell line BV173 to tumour necrosis factor-alpha (TNF-alpha)-stimulated (E-selectin+) endothelial cells. We found that the adhesion of these cells could be inhibited significantly by mAb HECA-452, in a similar fashion to CSLEX1, a mAb specific for E-selectin ligand sialyl Lewisx. This inhibiting effect of both mAb on the adhesion of polymorphonuclear leucocytes (PMN) and BV173 could only be demonstrated when the assay was performed at 4 degrees, but not at 37 degrees. Furthermore, using immunohistochemical analysis we found that the mAb HECA-452-reactive epitope is different from that recognized by CSLEX1. The present results give direct evidence that the antigen recognized by HECA-452 is involved in the adhesion of leucocytes to endothelial cells, although this antigenic epitope is different from that reactive to CSLEX1.     

A novel mechanism of immune regulation: interferon-gamma regulates retention of CD4 T cells during delayed type hypersensitivity

The local immune response is characterized by an increase in the rate of entry of lymphocytes from the blood into regional lymph nodes and changes in the output of cells in lymph. While significant data are available regarding the role of inflammation-induced vascular adhesion processes in regulating lymphocyte entry into inflamed tissues and lymph nodes, relatively little is known about the molecular processes governing lymphocyte exit into efferent lymph. We have defined a novel role for lymphatic endothelial cells in the regulation of lymphocyte exit during a delayed type hypersensitivity (DTH) response to mycobacterial purified protein derivative (PPD). Soluble, pro-adhesive factors were identified in efferent lymph concomitant with reduced lymphocyte output in lymph, which significantly increased lymphocyte binding to lymphatic endothelial cells. While all lymphocyte subsets were retained, CD4+ T cells appeared less susceptible than others. Among a panel of cytokines in inflammatory lymph plasma, interferon (IFN)-gamma alone appeared responsible for this retention. In vitro adhesion assays using physiological levels of IFN-gamma confirmed the interaction between recirculating lymphocytes and lymphatic endothelium. These data demonstrate a new level of immune regulation, whereby the exit of recirculating lymphocytes from lymph nodes is selectively and sequentially regulated by cytokines in a manner equally as complex as lymphocyte recruitment.     

Lymphocyte-Endothelial Interactions in Inflamed Synovia:Involvement of Several Adhesion Molecules and Integrin Epitopes

The role of several adhesion molecules for lymphocyte endothelial interactions in the synovia of rheumatoid arthritis patients was studied using the frozen section assay. Partial inhibition of lymphocyte binding to endothelium of synovial sections could be observed with antibodies against CD44, L-selectin, and β₁- and β₂-integrins, pointing to the participation of several adhesion molecules in the regulation of lymphocyte immigration into inflamed synovia rather than the presence of a unique homing receptor. Different degrees of inhibition were found within a series of antibodies against α₄ and β₁-integrins known to have functional effects in other interaction systems. In addition, increased binding to endothelial cells was induced when lymphocytes were pretreated with TS2/16 anti-β₁ IgG, whereas binding to non-endothelial components of synovia was increased after treatment with HP 2/4 (anti-α₄) Fab. The data suggest a multifunctional role of α/β₁-integrins in directly mediating adhesion as well as regulating adhesive interactions in the rheumatoid synovia.     

L-selectin and intercellular adhesion molecule 1 mediate lymphocyte migration to the inflamed airway/lung during an allergic inflammatory response in an animal model of asthma

T lymphocytes play a critical role in the development of allergic inflammation in asthma. Early in the allergic response, T lymphocytes migrate from the circulation into the lung to initiate and propagate airway inflammation. The adhesion molecules that mediate lymphocyte entry into inflamed lung have not been defined. This study directly examined the roles of L-selectin and intercellular adhesion molecule 1 (ICAM-1) in lymphocyte migration to the lung during an allergic inflammatory response in an animal model of asthma. Short-term (1 hour) in vivo migration assays and various combinations of adhesion molecule-deficient and wild-type mice were used. Migration of in vivo activated lymphocytes into inflamed lung was significantly greater than entry of resting lymphocytes into noninflamed lung (24.5% +/- 2.7% vs 9.5% +/- 1.3%, P =.001). Migration of activated lymphocytes into inflamed lung was inhibited by 30% in the absence of L-selectin (17.3% +/- 1.3%, P =.04), 47% in the absence of cell surface ICAM-1 (13.0% +/- 2.5%, P =.01), and 47% in the absence of endothelial ICAM-1 (13.0% +/- 2.5%, P =.01). Loss of ICAM-1 on both lymphocytes and lung endothelium inhibited lymphocyte migration by 60% (9.8% +/- 1.8%, P =.002). These findings demonstrate clear roles for both L-selectin and ICAM-1 in lymphocyte migration to the lung during an allergic inflammatory response, with ICAM-1 playing a greater role.