Lymphocyte trafficking and regional immunity

CCR9-positive lymphocytes and thymus-expressed chemokine distinguish small bowel from colonic Crohn's disease

BACKGROUND & AIMS

Thymus-expressed chemokine (TECK) or CCL25) is selectively expressed in the small bowel (SB), where lamina propria lymphocytes (LPL) and intraepithelial leukocyte expressing the cognate chemokine receptor CCR9 predominate. We characterize the role of TECK and CCR9-expresing lymphocytes in small intestinal Crohn's disease.

METHODS

CCR9 expression on lymphocytes from lamina propria, mesenteric lymph node, and peripheral blood was analyzed by flow cytometry and by Northern blotting for LPL. TECK expression was analyzed in inflamed SB and colon by reverse-transcription polymerase chain reaction and immunohistochemistry.

RESULTS

The fraction of CCR9(+) T cells in inflamed SB was significantly lower than in uninvolved SB mucosa. In contrast, in peripheral blood lymphocytes, CCR9(+) lymphocytes were markedly elevated in patients with small bowel Crohn's or celiac disease, but not in patients with purely colonic Crohn's. Also, TECK expression is altered in inflamed small bowel, being intensely expressed in a patchy distribution in crypt epithelial cells in proximity to lymphocytic infiltrates. TECK is not expressed in either normal or inflamed colon.

CONCLUSIONS

In SB immune-mediated diseases, there is repartitioning of CCR9(+) lymphocytes between SB and blood and an altered pattern of TECK expression in SB Crohn's. The TECK/CCR9 ligand/receptor pair may play an important role in the pathogenesis of SB Crohn's disease.

Leucocyte recruitment during enteric nematode infection

Resolution of infection with the intestinal nematode Trichinella spiralis depends on the host mounting a T helper 2 (Th2) response. It is known that both mast cells and T cells play a crucial role. We have previously shown that efficient migration of mast cells to the gut during infection depends on their expression of the integrin beta 7. beta 7 forms a heterodimer complex with either alpha E or alpha 4 integrin chains, alpha E beta 7 binding to E-cadherin expressed by epithelial cells and alpha 4 beta 7 binding to mucosal addressin cell adhesion molecule (MAdCAM-1) on the endothelium. We were interested to know whether dysfunctional mast cell localization to the gut in the absence of beta 7 was due to the failure of alpha 4 beta 7 to bind to MAdCAM-1 or the failure of alpha E beta 7 to bind to E-cadherin. We used blocking monoclonal antibodies against alpha E (M290) or alpha 4 (PS2) or beta 7 (HB293) during T. spiralis infection of C57BL/6 mice and found that all antibody treatments reduced mastocytosis. In contrast, none of the antibody treatments prevented the migration of CD3(+) T cells into the intestine. These results indicate that during inflammation (a) there is integrin redundancy for lymphocytes but not for mast cells and (b) both alpha E beta 7 and alpha 4 beta 7 are crucial either for the entry of mast cells into the gut or for their maturation once they have entered.

Neutrophils, monocytes, and dendritic cells express the same specialized form of PSGL-1 as do skin-homing memory T cells: cutaneous lymphocyte antigen

Memory T cells in inflamed skin express the cutaneous lymphocyte-associated antigen (CLA), a glycosylated epitope defined by the mAb HECA-452. We previously reported that on T cells, CLA occurs almost exclusively on the protein backbone of P-selectin glycoprotein ligand-1 (PSGL-1). T cells exhibiting the CLA isoform of PSGL-1 can tether and roll on both E- and P-selectin, while T cells expressing PSGL-1 without the CLA epitope do not bind E-selectin, though they may bind P-selectin. We show here that circulating neutrophils and monocytes, and cultured blood dendritic cells, also express CLA almost entirely as an isoform of PSGL-1. These cells all tether and roll on both E- and P-selectin. A chimeric fusion protein incorporating the 19 N-terminal amino acids of mature PSGL-1 exhibited HECA-452 immunoreactivity and supported rolling of CHO cells expressing either E- or P-selectin. These findings indicate a site for the CLA modification within the distal tip of PSGL-1, previously shown to be critical for P-selectin binding and to mediate some, but not all, of the E-selectin binding of PSGL-1. We hypothesize that the types of circulating leukocytes discussed above all use CLA/PSGL-1 to tether and roll on E- and P-selectin along the vascular endothelium.

Importance of primary capture and L-selectin-dependent secondary capture in leukocyte accumulation in inflammation and atherosclerosis in vivo

In the multistep process of leukocyte extravasation, the mechanisms by which leukocytes establish the initial contact with the endothelium are unclear. In parallel, there is a controversy regarding the role for L-selectin in leukocyte recruitment. Here, using intravital microscopy in the mouse, we investigated leukocyte capture from the free flow directly to the endothelium (primary capture), and capture mediated through interactions with rolling leukocytes (secondary capture) in venules, in cytokine-stimulated arterial vessels, and on atherosclerotic lesions in the aorta. Capture was more prominent in arterial vessels compared with venules. In venules, the incidence of capture increased with increasing vessel diameter and wall shear rate. Secondary capture required a minimum rolling leukocyte flux and contributed by approximately 20-50% of total capture in all studied vessel types. In arteries, secondary capture induced formation of clusters and strings of rolling leukocytes. Function inhibition of L-selectin blocked secondary capture and thereby decreased the flux of rolling leukocytes in arterial vessels and in large (>45 microm in diameter), but not small (<45 microm), venules. These findings demonstrate the importance of leukocyte capture from the free flow in vivo. The different impact of blockage of secondary capture in venules of distinct diameter range, rolling flux, and wall shear rate provides explanations for the controversy regarding the role of L-selectin in various situations of leukocyte recruitment. What is more, secondary capture occurs on atherosclerotic lesions, a fact that provides the first evidence for roles of L-selectin in leukocyte accumulation in atherogenesis.

Subspecialization of CXCR5+ T cells: B helper activity is focused in a germinal center-localized subset of CXCR5+ T cells

The T helper (Th) cell pool is composed of specialized cells with heterogeneous effector functions. Apart from Th1 and 2 cells, CXCR5+ T cells have been suggested to be another type of effector T cell specialized for B cell help. We show here that CXCR5+ T cells are heterogeneous, and we identify subsets of CXCR5+ CD4 T cells that differ in function and microenvironmental localization in secondary lymphoid tissues. CD57+CXCR5 T cells, hereafter termed germinal center Th (GC-Th) cells, are localized only in GCs, lack CCR7, and are highly responsive to the follicular chemokine B lymphocyte chemoattractant but not to the T cell zone EBI1-ligand chemokine. Importantly, GC-Th cells are much more efficient than CD57-CXCR5+ T cells or CXCR5- T cells in inducing antibody production from B cells. Consistent with their function, GC-Th cells produce elevated levels of interleukin 10 upon stimulation which, with other cytokines and costimulatory molecules, may help confer their B cell helper activity. Our results demonstrate that CXCR5+ T cells are functionally heterogeneous and that the GC-Th cells, a small subset of CXCR5+ T cells, are the key helpers for B cell differentiation and antibody production in lymphoid tissues.

Production of MDC/CCL22 by human intestinal epithelial cells

The intestinal mucosa contains a subset of lymphocytes that produce Th2 cytokines, yet the signals responsible for the recruitment of these cells are poorly understood. Macrophage-derived chemokine (MDC/CCL22) is a recently described CC chemokine known to chemoattract the Th2 cytokine producing cells that express the receptor CCR4. The studies herein demonstrate the constitutive production of MDC/CCL22 in vivo by human colon epithelium and by epithelium of human intestinal xenografts. MDC/CCL22 mRNA expression and protein secretion was upregulated in colon epithelial cell lines in response to proinflammatory cytokines or infection with enteroinvasive bacteria. Inhibition of nuclear factor (NF)-kappaB activation abolished MDC/CCL22 expression in response to proinflammatory stimuli, demonstrating that MDC/CCL22 is a NF-kappaB target gene. In addition, tumor necrosis factor-alpha-induced MDC/CCL22 secretion was differentially modulated by Th1 and Th2 cytokines. Supernatants from the basal, but not apical, side of polarized epithelial cells induced a MDC/CCL22-dependent chemotaxis of CCR4-positive T cells. These studies demonstrate the constitutive and regulated production by intestinal epithelial cells of a chemokine known to function in the trafficking of T cells that produce anti-inflammatory cytokines.

Preferential production of interferon-gamma by CD4+ T cells expressing the homing receptor integrin alpha4/beta7

Recent studies indicate that T helper type 1 (Th1) and 2 (Th2) lymphocytes differ in their expression of molecules that control T-cell migration, including adhesion molecules and chemokine receptors. We investigated the relationship between cytokine production and expression of the homing receptor integrin alpha4/beta7 on T cells. We began by analysing cytokine production by human CD4+ CD45RA- memory/effector T cells following brief (4 hr) stimulation with phorbol 12-myristate 13-acetate (PMA) and ionomycin. alpha4/ beta7high CD4+ T cells were more likely to produce the Th1 cytokine interferon-gamma (IFN-gamma) than were alpha4/beta7- CD4+ T cells in all six subjects studied. In contrast, production of the Th2 cytokine interleukin-4 (IL-4) was similar on alpha4/ beta7high and alpha4/beta7- CD4+ T cells. In addition, we found that human CD4+ CD45RA- T cells that adhered to the alpha4/beta7 ligand mucosal addressin cell adhesion molecule-1 (MAdCAM-1) had a greater capacity to produce IFN-gamma than did non-adherent cells, suggesting that the association between alpha4/beta7 expression and IFN-gamma production has functional significance. These results suggested that primary activation under Th1-promoting conditions might favour expression of alpha4/beta7. We directly examined this possibility, and found that naïve murine CD4+ T cells activated under Th1-promoting conditions expressed higher levels of alpha4/beta7 compared to cells activated under Th2-promoting conditions. The association between alpha4/beta7 expression and IFN-gamma production by CD4+ T cells may help to determine the cytokine balance when MAdCAM-1 is expressed at sites of inflammation in the intestine or elsewhere.

Fever-range hyperthermia dynamically regulates lymphocyte delivery to high endothelial venules

Fever is associated with increased survival during acute infection, although its mechanism of action is largely unknown. This study found evidence of an unexpectedly integrated mechanism by which fever-range temperatures stimulate lymphocyte homing to secondary lymphoid tissues by increasing L-selectin and alpha4beta7 integrin-dependent adhesive interactions between circulating lymphocytes and specialized high endothelial venules (HEV). Exposure of splenic lymphocytes in vivo to fever-like whole-body hyperthermia (WBH; 39.8 +/- 0.2 degrees C for 6 hours) stimulated both L-selectin and alpha4beta7 integrin-dependent adhesion of lymphocytes to HEV under shear conditions in lymph nodes and Peyer patches. The adhesiveness of HEV ligands for L-selectin and alpha4beta7 integrin (ie, peripheral lymph node addressin and mucosal addressin cell adhesion molecule-1) also increased during WBH or febrile responses associated with lipopolysaccharide-induced or turpentine-induced inflammation. Similar increases in HEV adhesion occurred during hyperthermia treatment of lymph node and Peyer patch organ cultures in vitro, indicating that the local lymphoid tissue microenvironment is sufficient for the hyperthermia response. In contrast, WBH did not augment adhesion in squamous endothelium of nonlymphoid tissues. Analysis of homing of alpha4beta7(hi) L-selectin(lo) murine TK1 cells and L-selectin(hi) alpha4beta7 integrin-negative 300.19/L-selectin transfectant cells showed that fever-range temperatures caused a 3- to 4-fold increase in L-selectin and alpha4beta7 integrin-dependent trafficking to secondary lymphoid tissues. Thus, enhanced lymphocyte delivery to HEV by febrile temperatures through bimodal regulation of lymphocyte and endothelial adhesion provides a novel mechanism to promote immune surveillance.

Antibody binding to a conformation-dependent epitope induces L-selectin association with the detergent-resistant cytoskeleton

L-Selectin mediates leukocyte rolling on endothelium and immobilized leukocytes. Its regulation has been the subject of much study, and the conformation of the molecule may play an important role in its function. Here we report that a conformational change in L-selectin, induced by an anti-lectin domain mAb (LAM1-116) and recognized by another mAb directed to a conserved epitope on L-selectin (EL-246), predisposed L-selectin to cytoskeletal association. This effect was due to direct binding of the mAb, not to overt signaling events, and was specific to LAM1-116. Nineteen other anti-L-selectin mAbs directed against the lectin, epidermal growth factor, or short consensus repeat domains lacked this activity. The induced conformational change occurred at 37 degrees C, at 4 degrees C, in the presence of sodium azide and tyrosine kinase inhibitors herbimycin A and genistein, and with soluble detergent-extracted L-selectin. In the presence of LAM1-116, EL-246 induced cytoskeletal association of L-selectin in the absence of Ab cross-linking as visualized by L-selectin staining after low dose detergent treatment of the cells. We propose that the conformational change described herein regulates L-selectin-mediated events by exposing a high avidity binding site that, when engaged, triggers association of L-selectin with the cytoskeleton, which may lead to stronger tethers with physiological ligands.

Human leukocyte subpopulations from inflamed gut bind to joint vasculature using distinct sets of adhesion molecules

Reactive arthritis can be triggered by inflammatory bowel diseases. We hypothesized that migration of mucosal immune cells from inflamed gut to joints could contribute to the development of reactive arthritis. Here we isolated gut-derived leukocytes from patients with Crohn's disease and ulcerative colitis. Using function-blocking mAbs and in vitro frozen section adhesion assays we studied whether these cells bind to synovial vessels and which molecules mediate the interaction. The results showed that mucosal leukocytes from inflammatory bowel diseased gut bind well to venules in synovial membrane. Small intestinal lymphocytes adhered to synovial vessels using multiple homing receptors and their corresponding endothelial ligands (CD18-ICAM-1, alpha(4)beta(7)/alpha(4)beta(1)-integrin-VCAM-1, L-selectin-peripheral lymph node addressins, and CD44). Of these, only ICAM-1 significantly supported binding of immunoblasts. In contrast, P-selectin glycoprotein ligand-1-P-selectin interaction accounted for practically all synovial adherence of mucosal macrophages. In addition, blocking of vascular adhesion protein-1 significantly inhibited binding of all these leukocyte subsets to joint vessels. We conclude that different leukocyte populations derived from inflamed gut bind avidly to synovial vessels using distinct repertoire of adhesion molecules, suggesting that their recirculation may contribute to the development of reactive arthritis in inflammatory bowel diseases.

Regulated MIP-3alpha/CCL20 production by human intestinal epithelium: mechanism for modulating mucosal immunity

Human intestinal epithelial cells secrete an array of chemokines known to signal the trafficking of neutrophils and monocytes important in innate mucosal immunity. We hypothesized that intestinal epithelium may also have the capacity to play a role in signaling host adaptive immunity. The CC chemokine macrophage inflammatory protein (MIP)-3alpha/CCL20 is chemotactic for immature dendritic cells and CD45RO(+) T cells that are important components of the host adaptive immune system. In these studies, we demonstrate the widespread production and regulated expression of MIP-3alpha by human intestinal epithelium. Several intestinal epithelial cell lines were shown to constitutively express MIP-3alpha mRNA. Moreover, MIP-3alpha mRNA expression and protein production were upregulated by stimulation of intestinal epithelial cells with the proinflammatory cytokines tumor necrosis factor-alpha or interleukin-1alpha or in response to infection with the enteric bacterial pathogens Salmonella or enteroinvasive Escherichia coli. In addition, MIP-3alpha was shown to function as a nuclear factor-kappaB target gene. In vitro findings were paralleled in vivo by increased expression of MIP-3alpha in the epithelium of cytokine-stimulated or bacteria-infected human intestinal xenografts and in the epithelium of inflamed human colon. Mucosal T cells, other mucosal mononuclear cells, and intestinal epithelial cells expressed CCR6, the cognate receptor for MIP-3alpha. The constitutive and regulated expression of MIP-3alpha by human intestinal epithelium is consistent with a role for epithelial cell-produced MIP-3alpha in modulating mucosal adaptive immune responses.

Fibroblasts regulate the switch from acute resolving to chronic persistent inflammation

Fibroblasts are important sentinel cells in the immune system and, here, it is proposed that these cells play a critical role in the switch from acute inflammation to adaptive immunity and tissue repair. It is suggested that chronic inflammation occurs because of disordered fibroblast behaviour in which failure to switch off their inflammatory programme leads to the inappropriate survival and retention of leukocytes within inflamed tissue.

Involvement of chemokine receptors in breast cancer metastasis

Breast cancer is characterized by a distinct metastatic pattern involving the regional lymph nodes, bone marrow, lung and liver. Tumour cell migration and metastasis share many similarities with leukocyte trafficking, which is critically regulated by chemokines and their receptors. Here we report that the chemokine receptors CXCR4 and CCR7 are highly expressed in human breast cancer cells, malignant breast tumours and metastases. Their respective ligands CXCL12/SDF-1alpha and CCL21/6Ckine exhibit peak levels of expression in organs representing the first destinations of breast cancer metastasis. In breast cancer cells, signalling through CXCR4 or CCR7 mediates actin polymerization and pseudopodia formation, and subsequently induces chemotactic and invasive responses. In vivo, neutralizing the interactions of CXCL12/CXCR4 significantly impairs metastasis of breast cancer cells to regional lymph nodes and lung. Malignant melanoma, which has a similar metastatic pattern as breast cancer but also a high incidence of skin metastases, shows high expression levels of CCR10 in addition to CXCR4 and CCR7. Our findings indicate that chemokines and their receptors have a critical role in determining the metastatic destination of tumour cells.

Integrin alpha E(CD103)beta 7 mediates adhesion to intestinal microvascular endothelial cell lines via an E-cadherin-independent interaction

Integrins are important for T cell interactions with endothelial cells. Because the integrin alpha(E)beta(7) is expressed on some circulating gut-homing T cells and as T cell numbers are reduced in the intestinal lamina propria of alpha(E)-deficient mice, we evaluated whether alpha(E)beta(7) mediates binding to intestinal endothelial cells. We found that anti-alpha(E)beta(7) mAbs partially blocked the binding of cultured intraepithelial T cells to human intestinal microvascular endothelial cells (HIMEC). Furthermore, alpha(E)beta(7)-transfected K562 cells bound more efficiently than vector-transfected K562 cells to HIMEC. Finally, HIMEC bound directly to an alpha(E)beta(7)-Fc fusion protein. These interactions were partially blocked by anti-alpha(E)beta(7) mAbs, and endothelial cell binding to the alpha(E)beta(7)-Fc was dependent upon the metal ion-dependent adhesion site within the alpha(E) A domain. Of note, the HIMEC lacked expression of E-cadherin, the only known alpha(E)beta(7) counterreceptor as assessed by functional studies, flow cytometry, and RT-PCR. Thus, HIMEC/alpha(E)beta(7) binding was independent of E-cadherin. In addition, this interaction appeared to be tissue selective, as HIMEC bound to the alpha(E)beta(7)-Fc, whereas microvascular endothelial cells from the skin did not. Finally, there was evidence for an alpha(E)beta(7) ligand on intestinal endothelial cells in vivo, as alpha(E)beta(7) expression enhanced lymphocyte binding around vessels in the lamina propria in tissue sections. Thus, we have defined a novel interaction for alpha(E)beta(7) at a nonepithelial location. These studies suggest a role for alpha(E)beta(7) in interactions with the intestinal endothelium that may have implications for intestinal T cell homing or functional responses.

Intratumoral injection of lipopolysaccharide causes regression of subcutaneously implanted mouse glioblastoma multiforme

OBJECTIVE

Anecdotal reports documented extended survival times for patients who developed infections at the site of resection of malignant gliomas. Hypothesized mechanisms for this phenomenon include immune responses triggered by lipopolysaccharide (LPS). This investigation assessed whether LPS could produce tumor regression in an in vivo model of malignant glioma.

METHODS

Delayed brain tumor cells (2 x 10(6)) were injected subcutaneously into female BALB/c mice. LPS (300-500 microg) was injected intratumorally or subcutaneously at a contralateral site on Days 10, 17, and 24. Control animals received phosphate-buffered saline intratumorally or subcutaneously. Mice were killed on Day 28, and tumors were removed. Mean tumor masses for control animals and the two LPS-treated groups (intratumoral or contralateral subcutaneous treatment) were compared. Histological assessments of treated and control tumors were performed.

RESULTS

Complete or nearly total tumor regression was achieved in all 20 mice with subcutaneous delayed brain tumor cell tumors treated intratumorally with 400 microg of LPS (mean tumor mass of 0.09 +/- 0.38 g versus 2.42 +/- 2.46 g for control animals, P < 0.0001). Intratumoral administration of 300 microg of LPS or subcutaneous injection of 300 or 400 microg of LPS at a contralateral site resulted in less consistent regression of subcutaneous tumors. Administration of 500 microg of LPS resulted in tumor regression similar to that observed with lower doses but was limited by treatment-related deaths in 40% of animals. Histological assessment revealed lymphocytic infiltration of LPS-treated tumors.

CONCLUSION

Intratumoral injections of LPS caused dramatic regression of subcutaneously implanted delayed brain tumor cell mouse gliomas. Investigation of this antitumoral effect may improve treatment responses for patients with malignant gliomas.

Bonzo/CXCR6 expression defines type 1-polarized T-cell subsets with extralymphoid tissue homing potential

Chemokine receptor expression is finely controlled during T-cell development. We show that newly identified chemokine receptor Bonzo/CXCR6 is expressed by subsets of Th1 or T-cytotoxic 1 (Tc1) cells, but not by Th2 or Tc2 cells, establishing Bonzo as a differential marker of polarized type 1 T cells in vitro and in vivo. Priming of naive T cells by dendritic cells induces expression of Bonzo on T cells. IL-12 enhances this dendritic cell-dependent upregulation, while IL-4 inhibits it. In blood, 35-56% of Bonzo+ CD4 T cells are Th1 cells, and 60-65% of Bonzo+ CD8 T cells are Tc1 cells, while few Bonzo+ cells are type 2 T cells. Almost all Bonzo+ Tc1 cells contain preformed granzyme A and display cytotoxic effector phenotype. Most Bonzo+ T cells lack L-selectin and/or CCR7, homing receptors for lymphoid tissues. Instead, Bonzo+ T cells are dramatically enriched among T cells in tissue sites of inflammation, such as rheumatoid joints and inflamed livers. Bonzo may be important in trafficking of effector T cells that mediate type 1 inflammation, making it a potential target for therapeutic modulation of inflammatory diseases.

Expression of chemokine receptors by lung T cells from normal and asthmatic subjects

The lung is an important tertiary lymphoid organ with constant trafficking of T cells through the lung in both health and disease. T cell migration is controlled by a combination of adhesion receptors and chemokines expressed on vascular endothelium and in the tissue, often in an organ-specific manner. This leads to selective accumulation of different T cell subsets, a process called lymphocyte homing. There is evidence for a distinct lung-homing pathway, but no specific lung-homing receptors have been described. We analyzed the chemokine receptor profile of lung T cells to determine the extent to which lung T cells shared homing pathways with other organs such as the gut and skin. In addition, we compared expression of receptors in normal and asthmatic individuals to determine whether different pathways were used in health and disease. We observed that lung T cells expressed a profile of chemokine and adhesion receptors distinct from that of gut- and skin-homing T cells although no chemokine receptor specific for the lung was found. In particular, lung T cells expressed CCR5 and CXCR3, but not CCR9 or cutaneous lymphocyte Ag, and only low levels of CCR4 and alpha(4)beta(7). No differences were observed between lung T cells from normal vs asthmatic subjects. This study provides added support for the concept of a lung-homing pathway separate from other mucosal organs such as the gut and suggests that the chemokine pathways that control T cell migration in normal homeostasis and Th2-type inflammatory responses are similar.

Lymphocyte traffic control by chemokines

In contrast to the remarkable chemokine responses of phagocytes and monocytes that were documented early on, lymphocytes have been considered for a long time to be poor targets for chemokine action. This view has changed dramatically with the discovery that peripheral blood T cells need to be activated before they can migrate in response to inflammatory chemokines. These chemokines do not act on the bulk of resting T cells that are in circulation. The identification of a new group of chemokines that selects resting, as opposed to effector, T and B cells was very exciting. These inflammation-unrelated chemokines affect transendothelial migration and localization of progenitor and mature lymphocytes in lymphoid and nonlymphoid tissues. Here, we summarize the current view of chemokine-mediated lymphocyte traffic and focus on the molecular mechanisms by which T cell responses to chemokines are modulated. Recent developments in this area justify the hypothesis that the distinct migration patterns of lymphocytes throughout their life cycle--that is, during lymphopoiesis, antigen-dependent priming, inflammation and immune surveillance--are finely tuned by changing sets of chemokines that are selective for developmentally regulated chemokine receptors. Thus, the chemokine system assures that cell traffic during inflammatory responses occurs in the proper spatial and temporal fashion and disturbance of this system, therefore, can lead to inflammatory disease.

CCR7 expression and memory T cell diversity in humans

CCR7, along with L-selectin and LFA-1, mediates homing of T cells to secondary lymphoid organs via high endothelial venules (HEV). CCR7 has also been implicated in microenvironmental positioning of lymphocytes within secondary lymphoid organs and in return of lymphocytes and dendritic cells to the lymph after passage through nonlymphoid tissues. We have generated mAbs to human CCR7, whose specificities correlate with functional migration of lymphocyte subsets to known CCR7 ligands. We find that CCR7 is expressed on the vast majority of peripheral blood T cells, including most cells that express adhesion molecules (cutaneous lymphocyte Ag alpha(4)beta(7) integrin) required for homing to nonlymphoid tissues. A subset of CD27(neg) memory CD4 T cells from human peripheral blood is greatly enriched in the CCR7(neg) population, as well as L-selectin(neg) cells, suggesting that these cells are incapable of homing to secondary lymphoid organs. Accordingly, CD27(neg) T cells are rare within tonsil, a representative secondary lymphoid organ. All resting T cells within secondary lymphoid organs express high levels of CCR7, but many activated cells lack CCR7. CCR7 loss in activated CD4 cells accompanies CXC chemokine receptor (CXCR)5 gain, suggesting that the reciprocal expression of these two receptors may contribute to differential positioning of resting vs activated cells within the organ. Lymphocytes isolated from nonlymphoid tissues (such as skin, lung, or intestine) contain many CD27(neg) cells lacking CCR7. The ratio of CD27(neg)/CCR7(neg) cells to CD27(pos)/CCR7(pos) cells varies from tissue to tissue, and may correlate with the number of cells actively engaged in Ag recognition within a given tissue.

8-Iso-PGF2 alpha induces beta 2-integrin-mediated rapid adhesion of human polymorphonuclear neutrophils: a link between oxidative stress and ischemia/reperfusion injury

F(2)-Isoprostanes are generated from a cyclooxygenase-independent oxidative modification of arachidonic acid. They are present in atherosclerotic plaques and are platelet activators as well as potent vasoconstrictors. Polymorphonuclear neutrophils are major players in ischemia/reperfusion injury and in restenosis after PTCA. The effects of 8-isoprostaglandin (PG) F(2alpha) on very rapid beta(2)-integrin-dependent adhesion was evaluated in human neutrophils in vitro by use of purified integrin as ligand. 8-Iso-PGF(2alpha) (1 nmol/L to 20 micromol/L) triggers a dose-dependent, very rapid neutrophil adhesion to human fibrinogen but not to the endothelial ligand intercellular adhesion molecule-1. Pretreatment with anti-ss(2)-integrin subtypes showed activation of CD11b/CD18 and CD11c/CD18. Adhesion triggering was completely prevented by pertussis toxin. SQ29,548, a specific antagonist of thromboxane A2 receptor, also dose-dependently prevented 8-iso-PGF(2alpha)-triggered neutrophil adhesion. 8-Iso-PGF(2alpha) did not trigger adhesion in human monocytes and lymphocytes and did not induce neutrophil chemotaxis or activation of the oxygen free-radical-forming enzyme NADPH-oxidase. These data highlight the role of 8-iso-PGF(2alpha) as a specific activator of rapid neutrophil adhesion and suggest its involvement in the pathogenesis of ischemia/reperfusion injury and in restenosis after PTCA. The effect is transduced via activation of the receptor for thromboxane A2.

C-C chemokine receptor 4 expression defines a major subset of circulating nonintestinal memory T cells of both Th1 and Th2 potential

CCR4, a chemokine receptor for macrophage-derived chemokine (MDC) and thymus and activation-regulated chemokine (TARC), has been implicated as a preferential marker for Th2 lymphocytes. Following in vitro polarization protocols, most Th2 lymphocytes express CCR4 and respond to its ligands TARC and MDC, whereas Th1 lymphocytes express CXC chemokine receptor 3 and CCR5 (but not CCR4). We show in this study that CCR4 is a major receptor for MDC and TARC on T lymphocytes, as anti-CCR4 mAbs significantly inhibit the migration of these cells to MDC and TARC. CCR4 is also highly expressed in most single-positive CD4(+) thymocytes and on a major fraction of blood nonintestinal (alpha(4)beta(7)(-)) memory CD4 lymphocytes, including almost all skin memory CD4(+) cells expressing the cutaneous lymphocyte Ag (CLA), but weakly or not expressed in other subsets in thymus and blood. Interestingly, major fractions of circulating CCR4(+) memory CD4 lymphocytes coexpress the Th1-associated receptors CXC chemokine receptor 3 and CCR5, suggesting a potential problem in using these markers for Th1 vs Th2 lymphocyte cells. Moreover, although production of Th2 cytokines in blood T cells is associated with CCR4(+) CD4 lymphocytes, significant numbers of freshly isolated circulating CCR4(+) memory CD4 lymphocytes (including both CLA(+) and CLA(-) fractions) readily express the Th1 cytokine IFN-gamma after short-term stimulation. Our results are consistent with a role for CCR4 as a major trafficking receptor for systemic memory T cells, and indicate that the patterns and regulation of chemokine receptor expression in vivo are more complex than indicated by current in vitro models of Th1 vs Th2 cell generation.

Cutting edge: C-C chemokine receptor 6 is essential for arrest of a subset of memory T cells on activated dermal microvascular endothelial cells under physiologic flow conditions in vitro

Memory T cells (mTC) express multiple chemokine receptors (including CCR4 and CCR6) that may potentially be involved in their arrest on inflamed endothelia. Herein, we specifically addressed whether CCR6 is required for mTC to arrest on TNF-alpha-activated human dermal microvascular endothelial cells (HDMEC) in vitro under shear stress conditions. Recombinant liver and activation-regulated chemokine (LARC)/CCL20 (a CCR6 ligand) induced firm arrest of cutaneous lymphocyte Ag(+) mTC in a flow chamber system using purified substrates. Strikingly, desensitization of CCR6 with LARC, but not thymus and activation-regulated chemokine/CCL17 or secondary lymphoid tissue chemokine/CCL21, caused a 50-75% decrease (p < 0. 001) in arrest of mTC on HDMEC, which was indistinguishable from the reduction observed when total mTC were treated with pertussis toxin (p > 0.5). CCR6-depleted mTC also had a markedly reduced ability to arrest on HDMEC. Our results suggest that LARC production by activated endothelial cells and CCR6 expression by mTC may be critical components in the pertussis toxin-sensitive arrest of mTC on activated HDMEC.

alpha(4)beta(7) independent pathway for CD8(+) T cell-mediated intestinal immunity to rotavirus

Rotavirus (RV), which replicates exclusively in cells of the small intestine, is the most important cause of severe diarrhea in young children worldwide. Using a mouse model, we show that expression of the intestinal homing integrin alpha(4)ss(7) is not essential for CD8(+) T cells to migrate to the intestine or provide immunity to RV. Mice deficient in ss7 expression (ss7(-/-)) and unable to express alpha(4)ss(7) integrin were found to clear RV as quickly as wild-type (wt) animals. Depletion of CD8(+) T cells in ss7(-/-) animals prolonged viral shedding, and transfer of immune ss7(-/-) CD8(+) T cells into chronically infected Rag-2-deficient mice resolved RV infection as efficiently as wt CD8(+) T cells. Paradoxically, alpha(4)ss(7)(hi) memory CD8(+) T cells purified from wt mice that had been orally immunized cleared RV more efficiently than alpha(4)ss(7)(low) CD8(+) T cells. We explained this apparent contradiction by demonstrating that expression of alpha(4)ss(7) on effector CD8(+) T cells depends upon the site of initial antigen exposure: oral immunization generates RV-specific CD8(+) T cells primarily of an alpha(4)ss(7)(hi) phenotype, but subcutaneous immunization yields both alpha(4)ss(7)(hi) and alpha(4)ss(7)(low) immune CD8(+) T cells with anti-RV effector capabilities. Thus, alpha(4)ss(7) facilitates normal intestinal immune trafficking to the gut, but it is not required for effective CD8(+) T cell immunity.

Chemokines trigger immediate beta2 integrin affinity and mobility changes: differential regulation and roles in lymphocyte arrest under flow

Chemokines trigger rapid integrin-dependent lymphocyte arrest to vascular endothelium. We show that the chemokines SLC, ELC, and SDF-1alpha rapidly induce lateral mobility and transient increase of affinity of the beta2 integrin LFA-1. Inhibition of phosphatidylinositol 3-OH kinase (PI(3)K) activity blocks mobility but not affinity changes and prevents lymphocyte adhesion to ICAM-1 immobilized at low but not high densities, suggesting that mobility enhances the frequency of encounters between high-affinity integrin and ligand but that at higher ligand density affinity changes are sufficient for arrest. Thus, chemokines trigger, through distinct signaling pathways, both a high-affinity state and lateral mobility of LFA-1 that can coordinately determine the vascular arrest of circulating lymphocytes under physiologic conditions.

De novo induction of endothelial L-selectin ligands during kidney allograft rejection

Acute kidney allograft rejection is characterized by a lymphocyte infiltration. L-selectin on lymphocytes and its endothelial glycosylated ligands are instrumental in the initiation of lymphocyte extravasation to sites of inflammation. From more than 500 core biopsy specimens taken from kidneys after transplantation, 250 biopsies were graded to have signs of acute rejection. Of these, 52 biopsies with various grades of histologic signs of acute rejection were selected for the study. Controls were 15 biopsies taken within 30 min after revascularization and 10 specimens from well-functioning allografts showing no clinical or histologic evidence of rejection. Immunochemical stainings with monoclonal antibodies against functionally active decorated L-selectin ligands. i.e., sialyl-Lewis x (sLex, 2F3 and HECA-452) or sulfated lactosamine (MECA-79) were performed. Although no endothelial 2F3 and MECA-79 epitopes were detected in nonrejecting control specimens, the expression was induced at the onset and during acute allograft rejections. The level of expression (in semi-quantitative score) of 2F3 reactivity correlated with the severity of rejection (P<0.0001, grade I versus grade IIB), and the level of expression decreased as the rejection resolved. Kidney biopsies taken shortly after revascularization and thus undergoing reperfusion injury showed endothelial staining with another anti sLex antibody, HECA-452. This staining disappeared from well-functioning grafts and reappeared at the onset of an acute allograft rejection. These results suggest that expression of functionally active, properly glycosylated L-selectin ligands might have a role in reperfusion injury and in the initiation of acute rejections after human kidney allograft transplantation.

The role of thymus-expressed chemokine and its receptor CCR9 on lymphocytes in the regional specialization of the mucosal immune system

Chemokines play an important role in the migration of leukocytes at sites of inflammation, and some constitutively expressed chemokines may direct lymphocyte trafficking within lymphoid organs and peripheral tissues. Thymus-expressed chemokine (TECK or Ckbeta-15/CCL25), which signals through the chemokine receptor CCR9, is constitutively expressed in the thymus and small intestine but not colon, and chemoattracts a small fraction of PBLs that coexpress the integrin alpha(4)beta(7). Here we show that TECK is expressed in the human small bowel but not colon by endothelial cells and a subset of cells in intestinal crypts and lamina propria. CCR9 is expressed in the majority of freshly isolated small bowel lamina propria mononuclear cells (LPMC) and at significantly higher levels compared with colonic LPMC or PBL. TECK was selectively chemotactic for small bowel but not colonic LPMC in vitro. The TECK-induced chemotaxis was sensitive to pertussis toxin and partially inhibited by Abs to CCR9. TECK attracts predominantly the T cell fraction of small bowel LPMC, whereas sorted CD3(+)CCR9(+) and CD3(+)CCR9(-) lymphocytes produce similar Th1 or Th2 cytokines at the single cell level. Collectively, our data suggest that the selective expression of TECK in the small bowel underlie the homing of CCR9(+) intestinal memory T cells to the small bowel rather than to the colon. This regional specialization implies a segregation of small intestinal from colonic immune responses.

Road signs guiding leukocytes along the inflammation superhighway

The term inflammation is used to describe the localized tissue changes, including leukocyte extravasation, that occur as part of the response to tissue damage, infection, or other immunologic responses. This carefully orchestrated series of events requires the existence of highly specific, regulated mechanisms for control of leukocyte recruitment and is dependent on both the inciting event and organ involved. This review summarizes recent developments in our understanding of how adhesion molecules and chemokines interact to facilitate tissue-specific and leukocyte subtype-specific influx during inflammation. Novel mechanisms believed to be responsible for capture and compartmentalization of B and T lymphocytes within lymph nodes are discussed, along with a description of adhesion molecule- and chemokine-mediated pathways that are believed to be involved in selective recruitment of lymphocytes and eosinophils to a variety of tissues, including the skin, gut, and lung. This growing knowledge and its potential importance provide enthusiasm for future anti-inflammatory therapies that target these recruitment pathways.

T-lymphocyte-epithelial-cell interactions: integrin alpha(E)(CD103)beta(7), LEEP-CAM and chemokines

The epithelia are the avascular layers of cells that cover the environment-exposed surfaces of the body. It appears that T cells localize to selected sites in or adjacent to epithelia via the selective expression of adhesion molecules and chemokine receptors on T cells. These bind to counter-receptors and to chemokines expressed by epithelial cells. Recently, there has been an advance in our understanding of the interaction of the alpha(Ebeta7) integrin with its epithelial cell ligand, E-cadherin. In addition, a new adhesion molecule has been identified on non-intestinal epithelial cells, termed lymphocyte-endothelial-epithelial-cell adhesion molecule (LEEP-CAM). Finally, there have been advances in our understanding of the role of skin- or gut-epithelia-derived chemokines in regulating activated T cell homing to these sites.

Induction of vascular adhesion protein-1 during liver allograft rejection and concomitant cytomegalovirus infection in rats

Vascular adhesion protein-1 (VAP-1) is an adhesion molecule controlling lymphocyte recirculation through high endothelial venules of the lymph nodes. It has also been shown to be induced and to mediate lymphocyte adhesion at sites of inflammation. We studied the expression of VAP-1 and two other inducible adhesion molecules ICAM-1 and VCAM-1 in our experimental model of rat liver allograft rejection and, in addition, the effect of concomitant rat cytomegalovirus (RCMV) infection on this expression. Expression of VAP-1, ICAM-1, and VCAM-1 was studied in rat liver allografts with or without RCMV infection, isografts, and normal rat liver. Immunoperoxidase technique and monoclonal antibodies including a novel anti-VAP-1 reagent were used. VAP-1 expression was induced by acute rejection in sinusoids, hepatocytes, and also in bile ducts, when compared to the isografts or normal liver, where only blood vessels were consistently positive. Sinusoidal and hepatocyte expression of VAP-1 was prolonged by the presence of RCMV. ICAM-1 and VCAM-1 expression was also induced by acute rejection. However, RCMV increased sinusoidal VCAM-1 expression compared to uninfected grafts. The present experimental study shows that VAP-1 is up-regulated in acute rejection of liver allografts, and that this up-regulation is prolonged by RCMV infection.

Expression of mucosal homing receptor alpha4beta7 is associated with enhanced migration to the Chlamydia-infected murine genital mucosa in vivo

The CD4 T helper cell type 1 (Th1) response is essential for the resolution of chlamydial genital infection in mice. However, not all Th1 clones are equally protective in eradicating the infection. Since oral immunization regimens produce protective immunity, we evaluated the role of the mucosa-associated homing receptor, alpha4beta7, in trafficking to the genital mucosa. Using a panel of CD4, Th1 cell lines and clones, we compared the lymphocyte homing patterns of a Chlamydia-specific, protective clone (P-MoPn), a nonprotective clone (N-MoPn), and a keyhole limpet hemocyanin (KLH)-specific cell line (KLH-1). T cells were labeled with the fluorescent dye PKH-26, adoptively transferred into Chlamydia-infected mice, and monitored at different time points throughout the course of a genital infection. We found that clones P-MoPn and N-MoPn migrated to similar extents to the genital tract and in significantly greater numbers than the KLH-specific T-cell line. Both clones and the KLH-1 line expressed similar levels of the adhesion molecules alpha4, beta1, CD44, and CD11a. However, clones P-MoPn and N-MoPn expressed higher levels of the mucosal homing receptor, alpha4beta7. Also, clones P-MoPn and N-MoPn but not the KLH-1 line migrated to the mesenteric lymph node, suggesting a mucosal recirculation pattern. Moreover, blocking alpha4beta7 adhesion interaction in vivo significantly reduced the recruitment of P-MoPn but not KLH-1 to the genital tract. These findings show that the mucosal homing receptor alpha4beta7 is utilized by a subset of CD4 cells during migration to the Chlamydia-infected genital tract.

An alpha-helical cationic antimicrobial peptide selectively modulates macrophage responses to lipopolysaccharide and directly alters macrophage gene expression

Certain cationic antimicrobial peptides block the binding of LPS to LPS-binding protein and reduce the ability of LPS to induce the production of inflammatory mediators by macrophages. To gain a more complete understanding of how LPS activates macrophages and how cationic peptides influence this process, we have used gene array technology to profile gene expression patterns in macrophages treated with LPS in the presence or the absence of the insect-derived cationic antimicrobial peptide CEMA (cecropin-melittin hybrid). We found that CEMA selectively blocked LPS-induced gene expression in the RAW 264.7 macrophage cell line. The ability of LPS to induce the expression of >40 genes was strongly inhibited by CEMA, while LPS-induced expression of another 16 genes was relatively unaffected. In addition, CEMA itself induced the expression of a distinct set of 35 genes, including genes involved in cell adhesion and apoptosis. Thus, CEMA, a synthetic alpha-helical peptide, selectively modulates the transcriptional response of macrophages to LPS and can alter gene expression in macrophages.

Lymphocyte CC chemokine receptor 9 and epithelial thymus-expressed chemokine (TECK) expression distinguish the small intestinal immune compartment: Epithelial expression of tissue-specific chemokines as an organizing principle in regional immunity

The immune system has evolved specialized cellular and molecular mechanisms for targeting and regulating immune responses at epithelial surfaces. Here we show that small intestinal intraepithelial lymphocytes and lamina propria lymphocytes migrate to thymus-expressed chemokine (TECK). This attraction is mediated by CC chemokine receptor (CCR)9, a chemoattractant receptor expressed at high levels by essentially all CD4(+) and CD8(+) T lymphocytes in the small intestine. Only a small subset of lymphocytes in the colon are CCR9(+), and lymphocytes from other tissues including tonsils, lung, inflamed liver, normal or inflamed skin, inflamed synovium and synovial fluid, breast milk, and seminal fluid are universally CCR9(-). TECK expression is also restricted to the small intestine: immunohistochemistry reveals that intense anti-TECK reactivity characterizes crypt epithelium in the jejunum and ileum, but not in other epithelia of the digestive tract (including stomach and colon), skin, lung, or salivary gland. These results imply a restricted role for lymphocyte CCR9 and its ligand TECK in the small intestine, and provide the first evidence for distinctive mechanisms of lymphocyte recruitment that may permit functional specialization of immune responses in different segments of the gastrointestinal tract. Selective expression of chemokines by differentiated epithelium may represent an important mechanism for targeting and specialization of immune responses.

CC chemokine receptor (CCR)2 is required for langerhans cell migration and localization of T helper cell type 1 (Th1)-inducing dendritic cells. Absence of CCR2 shifts the Leishmania major-resistant phenotype to a susceptible state dominated by Th2 cytokines, b cell outgrowth, and sustained neutrophilic inflammation

There is growing evidence that chemokines and their receptors regulate the movement and interaction of antigen-presenting cells such as dendritic cells (DCs) and T cells. We tested the hypothesis that the CC chemokine receptor (CCR)2 and CCR5 and the chemokine macrophage inflammatory protein (MIP)-1alpha, a ligand for CCR5, influence DC migration and localization. We found that deficiency of CCR2 but not CCR5 or MIP-1alpha led to distinct defects in DC biology. Langerhans cell (skin DC) density in CCR2-null mice was normal, and their ability to migrate into the dermis was intact; however, their migration to the draining lymph nodes was markedly impaired. CCR2-null mice had lower numbers of DCs in the spleen, and this was primarily due to a reduction in the CD8alpha(1) T helper cell type 1 (Th1)-inducing subset of DCs. Additionally, there was a block in the Leishmania major infection-induced relocalization of splenic DCs from the marginal zone to the T cell areas. We propose that these DC defects, in conjunction with increased expression of B lymphocyte chemoattractant, a B cell-specific chemokine, may collectively contribute to the striking B cell outgrowth and Th2 cytokine-biased nonhealing phenotype that we observed in CCR2-deficient mice infected with L. major. This disease phenotype in mice with an L. major-resistant genetic background but lacking CCR2 is strikingly reminiscent of that observed typically in mice with an L. major-susceptible genetic background. Thus, CCR2 is an important determinant of not only DC migration and localization but also the development of protective cell-mediated immune responses to L. major.

Chlamydia and associated arthritis

An inflammatory arthritis is known to follow urogenital infection with the intracellular bacterium Chlamydia trachomatis in some individuals, and recent research results have elucidated important aspects of the characteristics of this Chlamydia-associated joint disease. Although the several extra-articular features of Chlamydia-induced arthritis have been defined clinically, their detailed causes remain largely unexplained. Current data indicate that the clinical characteristics of joint disease associated with C. trachomatis infection and those associated with postenteric arthritis are not easily distinguishable, although the response of each to antibiotic therapy does differ. The biologic characteristics of Chlamydia and enteric organisms in the joint show profound differences, and these are probably responsible for the variable responses to drug treatment. Molecular analyses of synovial C. trachomatis have demonstrated that long-term infection of the joint occurs primarily in synovial tissue and that the organism exhibits highly unusual biologic properties in its synovial context. These unusual molecular, biochemical, and other characteristics provide explanations for the frequent culture negativity of joint materials for C. trachomatis and for several other aspects of the arthritogenic process. Much remains to be learned concerning the behavior of this organism in the joint and concerning its interaction with its synovial host cells.

Chemokines in tissue-specific and microenvironment-specific lymphocyte homing

This review describes recent breakthroughs in our understanding of the roles played by chemokines in lymphocyte trafficking. These include the first demonstration that chemokines control lymphocyte/vascular recognition by shear-resistant rapid adhesion; the first example of specialized tissue-specific homing mediated by chemokines; and the implication that chemokines may control microenvironmental segregation within lymphoid organs.

Cytokine and endothelial cell adhesion molecule expression in interleukin-10-deficient mice

The objectives of this study were to quantify cytokine mRNA levels and endothelial cell adhesion molecule message and protein expression in healthy wild-type and interleukin-10-deficient (IL-10(-/-)) mice that develop spontaneous and chronic colitis. We found that colonic message levels of IL-1, IL-6, tumor necrosis factor-alpha, interferon-gamma, lymphotoxin-beta, and transforming growth factor-beta were elevated in colitic mice 10- to 35-fold compared with their healthy wild-type controls. In addition, colonic message levels of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), and mucosal addressin cell adhesion molecule-1 (MAdCAM-1) were found to be increased 10-, 5-, and 23-fold, respectively, in colitic IL-10(-/-) mice compared with their wild-type controls. Immunoradiolabeling as well as immunohistochemistry revealed large and significant increases in vascular surface expression of colonic ICAM-1, VCAM-1, and MAdCAM-1 in the mucosa as well as the submucosa of the colons of colitic mice. These data are consistent with the hypothesis that deletion of IL-10 results in the sustained production of proinflammatory cytokines, leading to the upregulation of adhesion molecules and infiltration of mononuclear and polymorphonuclear leukocytes into the cecal and colonic interstitium.

Developmental switches in chemokine response profiles during B cell differentiation and maturation

Developing B cells undergo dramatic changes in their responses to chemoattractant cytokines (chemokines) and in expression of chemokine receptors. Bone marrow pre-pro-B cells (AA4.1(+)/natural killer 1.1(-) Fraction A cells) and cells capable of generating pro-B colonies in the presence of interleukin 7 and flt3 ligand migrate to thymus-expressed chemokine (TECK), a response lost in later stages of B cell development. B cell-attracting chemokine 1 (BCA-1) responses correlate with CXC chemokine receptor (CXCR)5 expression, are first displayed by a pro-B cell subset, are lost in pre-B cells, and then are regained just before and after egress from the marrow. All peripheral B cell subsets, including follicular and germinal center as well as marginal zone and peritoneal B1 B cells, respond to BCA-1, implying that responsiveness to this follicular chemokine is not sufficient to predict follicle localization. Responses to the CC chemokine receptor (CCR)7 ligands secondary lymphoid tissue chemoattractant (SLC) and macrophage inflammatory protein (MIP)-3beta, implicated in homing to lymphoid tissues, are upregulated before B cell exit from the marrow, but increase further in the periphery and are shared by all peripheral B cells. In contrast, responsiveness to MIP-3alpha and expression of CCR6 are acquired only after emigration to the periphery and during maturation into the recirculating B cell pool. Chemotaxis to stromal cell-derived factor 1alpha is observed at all stages of B cell differentiation. Thus, unique patterns of chemokine responses may help define developing B cell populations and direct their maturation in the marrow and migration to the periphery.

Development of intermediate-grade (mantle cell) and low-grade (small lymphocytic and marginal zone) human non-Hodgkin's lymphomas xenotransplanted in severe combined immunodeficiency mouse models

We have used severe combined immunodeficiency (SCID) (c.b.-17, ICR/SCID) mice to develop xenotransplantation (XT) models for human intermediate-and-low-grade non-Hodgkin's lymphomas (NHL). In the past, SCID mice have provided a variety of useful XT models for human hematopoietic neoplasms that primarily involve the acute leukemias and some nonhematopoietic tumors, but only rare reports exist on use of the SCID mouse model in the study of primary tumor cells from NHL. Intermediate-grade and low-grade NHL are the most common lymphomas seen in adults. There is no effective therapy for those types of NHL, and they have not been established in an animal model to date. The lack of an animal model has hampered studies that can evaluate the disease process in vivo as well as the definition of therapeutic parameters involved in treatment. We report in this study that primary patient samples of NHL ( intermediate grade and low grade) have been successfully established in SCID mice after XT. NHL include intermediate-grade (mantle cell lymphoma) and low-grade (eg, small lymphocytic lymphoma/chronic lymphocytic lymphoma and marginal zone lymphoma) forms. Studies have been directed toward creating appropriate conditions for the optimal grafting of these NHL in SCID mice so that the disease process in humans could be accurately simulated. These studies indicate that development of XT-human lymphoma cells in SCID mice appear to be linked to their biologic and/or clinical behavior, transplanted lymphoma cell number, and age, as well as to the natural killer cell status of the SCID mouse recipients. Evidence has also shown that NHL cells can exhibit homing or trafficking patterns in SCID recipients that resemble those observed in patients with gastrointestinal lymphomatous involvement (particularly that of mantle cell lymphoma). Our studies also indicate that artefactual influences, such as the outgrowth of Epstein-Barr virus-associated lymphoblastoid lesions, are rare occurrences in the human NHL/SCID models that we have established.

Immune-inflammatory mechanisms in IFNgamma-mediated anti-tumor activity

IFNgamma is a functionally pleiotropic cytokine which shows considerable potency in promoting anti-tumor functions in vivo. Despite limited efficacy when delivered systemically either to experimental animals or patients, IFNgamma appears to play an important and perhaps critical role in directing the development of immune-mediated tumor destruction when expressed within the tumor bed. This has been demonstrated both by use of tumor cells transduced to express IFNgamma and by the use of IL-12 which is able, at least is murine models, to promote an IFNgamma-dependent, T cell mediated anti-tumor response. Recent studies indicate that the therapeutic efficacy of IFNgamma in tumor models depends critically upon the ability of the tumor cells themselves to respond to IFNgamma. Though IFNgamma is able to induce anti-viral activity and has direct anti-proliferative effects on some tumor cell lines, immunomodulatory function also appears to be an important component of its anti-tumor action. This is mediated through the action of several different classes of IFNgamma-inducible gene expression which control antigen processing and presentation, leukocyte trafficking, and indirect tumor cytotoxicity.

The parting of the endothelium: miracle, or simply a junctional affair?

Leukocyte extravasation from the blood across the endothelium is vital for the functioning of the immune system. Our understanding of the early steps of this process has developed rapidly. However, it is still unclear how leukocytes undergo the final step, migrating through the junctions that mediate adhesion between adjacent endothelial cells, while preserving the barrier function of the endothelium. The first stage of transmigration - tethering and rolling - is mediated by interactions between selectins on the surface of leukocytes and glycosylated proteins such as GlyCAM-1 on the surface of endothelial cells. Stimulation of the leukocyte by chemokines then induces tight adhesion, which involves binding of activated leukocyte integrins to endothelial ICAM-1/VCAM-1 molecules. Passage of the leukocyte across the endothelium appears to require delocalization of certain endothelial cell molecules and proteolytic degradation of junctional complexes.

Cutting edge: a novel function for the SLAP-130/FYB adapter protein in beta 1 integrin signaling and T lymphocyte migration

The role of integrin-mediated signaling events in T cell function remains incompletely characterized. We report here that alpha4beta1 integrin stimulation of H9 T cells and normal human T cell blasts results in rapid and transient tyrosine phosphorylation of the adapter protein, SH2 domain-containing 76-kDa protein (SLP-76)-associated phosphoprotein of 130 kDa (SLAP-130)/FYB at levels comparable to those observed following TCR stimulation. Stimulation of T cells via the alpha4beta1 integrin enhances the association of tyrosine phosphorylated SLAP-130/FYB with the SH2 domain of the src tyrosine kinase p59fyn. Activation of normal T cells, but not H9 T cells, via alpha4beta1 leads to tyrosine phosphorylation of SLP-76 as well as SLAP-130/FYB. Overexpression of SLAP-130/FYB in normal T cells enhances T cell migration through fibronectin-coated filters in response to the chemokine stromal cell-derived factor (SDF)-1alpha. These results identify SLAP-130/FYB as a new tyrosine phosphorylated substrate in beta1 integrin signaling and suggest a novel function for SLAP-130/FYB in regulating T lymphocyte motility.

The role of chemokines in the microenvironmental control of T versus B cell arrest in Peyer's patch high endothelial venules

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)-3beta (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-3beta signaling, and occurs efficiently in SLC(low/-) 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.

Anti-CD43 Monoclonal Antibody L11 Blocks Migration of T Cells to Inflamed Pancreatic Islets and Prevents Development of Diabetes in Nonobese Diabetic Mice

Nonobese diabetic mice are a well-known model for human insulin-dependent diabetes mellitus. These mice develop autoimmune-mediated inflammation of the pancreatic islets, followed by destruction of the insulin-producing β cells and development of diabetes. Nonobese diabetic mice also have salivary gland inflammation, and serve as a model for human Sjogren’s syndrome. T cells are a prominent component of the inflammatory infiltrate in these sites, and T cell recruitment from the blood is thought to be essential for the initiation and maintenance of pathologic tissue damage. A unique mAb to murine CD43, L11, has recently been shown to block the migration of T cells from blood into organized lymphoid tissues. Here we demonstrate that L11 significantly inhibits T cell migration from blood into inflamed islets and salivary glands. Treatment of nonobese diabetic mice with L11 from 1 to 4 or 8 to 12 wk of age led to significant protection against the development of diabetes. Moreover, protection was long-lived, with decreased incidence of diabetes even months after cessation of Ab administration. When treatment was started at 1 wk of age, L11 inhibited the development of inflammation in pancreatic islets and salivary glands. L11 treatment had no long-term effect on numbers or phenotypes of peripheral lymphocytes. These data indicate that anti-CD43 Abs that block T cell migration may be useful agents for the prevention or treatment of autoimmune diseases including insulin-dependent diabetes mellitus and Sjogren’s syndrome.