Allograft tolerance induced by cyclophosphamide without prior inoculation of donor cells--immune suppression and redirection

OBJECTIVES

To determine the possibility and cellular mechanism of inducing allograft tolerance by multiple injection of a lower dose of cyclophosphamide without prior infusion of donor cells.

METHODS AND RESULTS

Heterotopic heart grafts were performed in MHC mismatched strain combinations (C57/B6 vs. BALB/c). Cyclophosphamide (40 mg/kg) was given intravenously on days 0, 2, 4 and 7 without prior infusion of donor cells. Long-term (> 100 days) allograft survival with normal histology was achieved. The long-term survivors accepted the donor skin grafts, but rejected the third-party skin grafts. Cyclophosphamide treatment initially led to profound lymphocytopenia, inhibition of spontaneous blastogenesis and low levels of lymphocyte proliferation response to both donor and third-party antigens. Ultimately, donor-specific tolerance occurred demonstrated by normal levels of peripheral lymphocytes, spontaneous blastogenesis and lymphocyte proliferation response to third-party antigens, and low levels of lymphocyte proliferation response to donor antigen. A switch of cytokines from IFNgamma dominant to IL-4 dominant, a low level of IgM and a high level of IgG1 were found in tolerant mice.

CONCLUSIONS

Allograft tolerance can be induced by a short course of cyclophosphamide without prior donor cell inoculation. Tolerance induced is characterized initially by non-specific immunosuppression, which progresses to donor-specific hyporesponsiveness associated with the development of a Th2 dominant cytokine response.

Opposing effects of rapamycin and cyclosporin A on activation-induced Ca(2+) release

Insofar as Ca(2+) plays a major role in T cell activation, we investigated the effect of the immunosuppressants cyclosporin A and rapamycin on T cell proliferation and on the activation-induced increase in [Ca(2+)](i). Both cyclosporin A and rapamycin inhibited mitogen (concanavalin A and phytohemagglutinin) and ionomycin+phorbol myristate acetate (PMA)-driven T cell proliferation (Ca(2+)-dependent). However, only rapamycin suppressed T cell proliferation stimulated by anti-CD28 antibody (Ab)+PMA, and recombinant interleukin-6-stimulated proliferation of the interleukin-6 dependent B9 cells (Ca(2+)-independent). These differences were associated with a different effect of both drugs on Ca(2+) release, as cyclosporin A attenuated while rapamycin augmented the mitogen-induced elevation in [Ca(2+)](i). Collectively, this supports the notion that Ca(2+) is required in early stages of T cell activation, and that cyclosporin A blocked only Ca(2+)-dependent while rapamycin blocked both Ca(2+)-dependent and -independent events of T cell activation.

CD45 modulation of CXCR1 and CXCR2 in human polymorphonuclear leukocytes

All leukocytes express the cell surface glycoprotein CD45, which has intrinsic intracellular protein tyrosine phosphatase activity. CD45 is known to play a regulatory role in activation-induced signaling in lymphocytes; however, little is known of its role in non-lymphoid leukocytes. Therefore, we examined the potential effect of CD45 on chemokine-induced signaling in human neutrophils (polymorphonuclear cells, PMN). Treating isolated PMN for 2 h with an anti-CD45RB antibody (Bra11) down-modulated expression of the chemokine receptors CXCR1 and CXCR2 to 44 +/- 10% and 47 +/- 9% of their respective controls. The tyrosine kinase inhibitors genistein and herbimycin A significantly inhibited the Bra11-induced down-modulation of CXCR1 and CXCR2. Furthermore, Bra11-treated PMN were functionally inhibited in their capacity to exhibit IL-8-induced transient intracellular Ca2+ increases. Selected targeting of CXC receptors is indicated by the fact that N-formyl-Met-Leu-Phe (fMLP) receptor expression and function were not lost following Bra11 treatment. The effect of Bra11 on IL-8-mediated function and receptor expression was paralleled by decreased tyrosine phosphorylation of a 54- to 60-kDa protein. These findings indicate that CD45 can act to modulate PMN responses to chemokines; thus agents regulating CD45 can potentially modulate leukocyte traffic and may represent a novel therapeutic approach towards the treatment of inflammatory diseases.

Cyclosporine inhibits long-term survival in cardiac allografts treated with monoclonal antibody against CD45RB

BACKGROUND

We have previously reported that a monoclonal antibody to CD45RB is a novel immunosuppressive agent; however, the optimal regimen in cardiac allografts remains unknown. The present study was undertaken to determine the optimal protocol of this therapy and its interaction with cyclosporine.

METHODS

A heterotopic heart allograft model was used in C57BL/6 to BALB/c mice. The following studies were conducted: 1) dose response study (low, intermediate, and high doses at 1, 3, and 9 mg/kg/day respectively), 2) short course (2 days) therapy vs. long course (9 days) therapy, 3) pretreatment (starting on day -1) vs no pretreatment, 4) daily therapy vs. alternative day therapy, and 5) monoclonal antibody treatment with and without cyclosporine.

RESULTS

The efficacy of the CD45RB monoclonal antibody was dose and duration dependent (p<0.01). Pretreatment significantly improved the efficacy of this therapy (74.5+/-13.4 days vs. 30.6+/-1.5 days, p<0.01). Daily therapy was superior to alternate day therapy (74.5+/-13.4 days vs. 30.4+/-1.5 days, p<0.03). Interestingly, we found that administration of cyclosporine prior to, at the same time as, or after administration of the CD45RB monoclonal antibody had a detrimental effect on graft survival compared to mAb treated alone (16.6+/-0.4 days, 25+/-2.3 days, and 35.3+/-0.9 days respectively vs. 74.5 days, p<0.01).

CONCLUSIONS

Immunosuppression with CD45RB monoclonal antibody is dose and duration dependent. Pretreatment and daily therapy improves results. Addition of cyclosporine inhibits long-term graft survival achieved by the monoclonal antibody alone.

Mechanisms of induction of renal allograft tolerance in CD45RB-treated mice

BACKGROUND

Rejection is the most significant problem in the field of transplantation. The current goal of transplant immunology is to develop better immunotherapeutic protocols that are aimed at specifically suppressing alloreactivity and preserving an otherwise intact immune system. We have previously shown that mice will accept renal allografts indefinitely with normal renal function after two injections of a monoclonal antibody to the CD45RB protein. Furthermore, this antibody will reverse acute rejection when therapy is delayed until day 4 and will still induce tolerance. The mechanisms of this therapeutic benefit are not known.

METHODS

BALB/C mice were used as recipients of major multiple histocompatibility complex-mismatched kidneys using C57BL/6 as donors. Immunoperoxidase microscopy and Northern blots for cytokine gene expression were used to study the renal allografts. Fluorescence-activated cell sorter (FACS) analyses of peripheral blood lymphocytes were performed. Phosphotyrosine peptide phosphatase assays were performed on splenic lymphocyte membranes.

RESULTS

A CD45RB monoclonal antibody (MB23G2) induced tolerance and partially depletes peripheral blood lymphocytes. A therapeutically ineffective CD45RB monoclonal antibody (MB4B4) merely coated the circulating lymphocytes. Furthermore, MB23G2 stimulated more tyrosine phosphatase activity than MB4B4 in mouse T-cell membranes.

CONCLUSIONS

The clearance of peripheral blood lymphocyte populations and stimulation of protein tyrosine phosphatase activity may be important in the mechanism of tolerance induction by CD45RB therapy, which may be clinically relevant in the therapy of organ rejection in humans.

Adoptively transferable tolerance induced by CD45RB monoclonal antibody

The phenomenon of rejection remains the most serious problem in transplantation. The ultimate goal in transplant immunology is to develop therapeutic strategies that lead to tolerance. It has been shown that two injections of a monoclonal antibody to CD45RB leads to indefinite acceptance of renal allografts in mice. Moreover, the CD45RB monoclonal antibody reverses acute rejection and still induces tolerance. The purpose of this study was to assess mechanisms that could underlie this therapeutic benefit. It was shown that splenic lymphocytes from tolerant animals augmented proliferation in allogeneic mixed lymphocyte reactions against donor alloantigens, and the serum of tolerant mice contained donor-specific antibodies, mainly of the IgG1 isotype, suggesting the presence of TH2 cytokines. Tolerance could not be broken by interleukin-2 infusion, but tolerance could be adoptively transferred by transfusion of tolerant mouse CD4+ splenic lymphocytes into naive allografted animals. These data suggest that an active immunoregulatory mechanism is partly responsible for the therapeutic effect. CD45RB-directed therapy may find clinical application in organ transplantation in human patients.

Enrichment of T cells carrying beta7 integrins in inflamed synovial tissue from patients with early spondyloarthropathy, compared to rheumatoid arthritis

OBJECTIVE

To compare the expression of adhesion molecules on synovial T cells from patients with early spondyloarthropathy (SpA) and rheumatoid arthritis (RA), with special reference to the beta7 integrins alpha4beta7 and alphaEbeta7 in view of their intimate association with intestinal tissue.

METHODS

Twenty-five synovial cell lines were generated by interleukin 2 (IL-2) expansion from synovial biopsies of patients with early SpA and RA, obtained from macroscopically inflamed synovial tissue by needle arthroscopy, and subsequently characterized by flow cytometry for CD3, CD4, CD8, L-selectin, CD11a, CD31, CD44, and alpha4beta7 and alphaEbeta7 integrin.

RESULTS

In SpA, the beta7 integrin expression was increased, compared to RA. Furthermore, an inverse relation between alpha4beta7 and alphaEbeta7 was present in SpA (r = -0.75, p < 0.02), as on many mucosal T cells. In contrast, an opposite correlation was noted in RA (r = +0.84, p < 0.01), as similarly described on a subset of circulating T cells.

CONCLUSION

Increased expression of beta7 integrins was noted on synovial T cell lines from SpA compared to RA, with discriminative correlations between alpha4beta7 and alphaEbeta7. This suggests a different origin of the synovial T cells in these diseases.

Distinctive activated cellular subsets in colon from patients with Crohn's disease and ulcerative colitis

BACKGROUND

Activated lymphocytes are considered to play a pathogenic role in Crohn's disease (CD) and ulcerative colitis (UC), although only a limited fraction of the gut-residing lymphocytes in these diseases may be pathogenetically involved, due to active recruitment from the peripheral circulation. Our aim was to characterize in situ preactivated lymphocytes in inflammatory bowel disease mucosa by expansion with interleukin-2.

METHODS

Flow cytometry was performed on T cells expanded from the colon of patients with CD (7), UC (16), and controls (20), with special reference to T-cell activation markers and adhesion molecules.

RESULTS

In CD a decrease in alpha4beta7 integrin expression was associated with an increase in alphaEbeta7. In UC a similar increase in alphaEbeta7 was observed. Moreover, L-selectin and CD30 were overexpressed on T helper cells in UC versus CD.

CONCLUSION

These findings indicate different immunopathogenic pathways for CD and UC.

Monoclonal antibody against CD45RB for the therapy of rejection and autoimmune diseases

Rejection continues to be the single largest impediment to successful organ transplantation. Current therapy, which must be taken for a lifetime is nonspecific and has significant side effects including infection and cancer. There is a need to develop improved means of immunosuppression. The current goal of transplantation immunology is to induce a prolonged state of nonreactivity to the allograft but preserving an otherwise intact immune system (tolerance). We have recently reported that a monoclonal antibody against CD45RB is a potent immunosuppressive agent, and that it induces donor specific tolerance in the mouse. In this contribution we briefly review our understanding of the molecular basis for the activity of this therapy and update results in various transplant and autoimmune disease animal models. The clinical relevance and future development of this novel therapy is also discussed.

Influence of residential fungal contamination on peripheral blood lymphocyte populations in children

Reported residential fungal contamination has been associated consistently with increased symptoms among occupants; however, an objective measure of a health effect is lacking, and a pathophysiologic mechanism has not been established. Our objective was to determine if exposure to indoor fungal contamination influenced T-cell differentiation. In this study, we contrasted lymphocyte populations, measured by flow cytometry, between a group of children who lived in homes with considerable fungal contamination (n = 39) and a group in less-contaminated homes (n = 20). Indicators of fungal biomass were viable fungi in house dust and air ergosterol in the child's bedroom. Living in a more-contaminated home versus a less-contaminated home was associated with a larger number of CD3+ T cells expressing CD45RO (1.5 x 10(9)/I versus 1.1 x 10(9)/I, respectively; p = .05, two-tailed t testing) and a reduced CD4/CD8 ratio (1.6 versus 1.8, respectively; p = .04). The differences persisted over a 12-mo period, and they were not explained by the child's age or total serum IgE, dust mite antigens, and the presence of furry or feathered pets or a humidifier. The results suggest that residential fungal contamination leads to chronic stimulation of children's lymphocytes.

Antibody-mediated targeting of CD45 isoforms: a novel immunotherapeutic strategy

CD45 is a family of transmembrane protein tyrosine phosphatases exclusively expressed by hematopoietic cells and critically involved in the regulation of T cell activation signals. We now demonstrate that three 100-microg doses of anti-CD45RB mAb MB23G2 can induce long-term engraftment of islets into major histcompatibility complex-disparate chemically diabetic mice. Long-term graft survivors (>120 days) were tolerant to new islet allografts from the original donor strain. MB23G2 induced a temporary decrease in number circulating leukocytes but had no effect on leukocyte number in other lymphoid compartments. Histologic examination of allografts from treated and untreated recipients revealed a similar peri-islet infiltration on day 6. Eleven days after transplant, the peri-islet infiltrate in treated animals persisted, but in marked contrast to untreated control animals, there was no insulitis and islet integrity was preserved. The peri-islet infiltrate from treated animals showed a mild increase in CD4 cells, a decrease in CD8 cells, and decreased intensity of CD45RB expression. Treatment of naive animals with anti-CD45RB (MB23G2) resulted in a shift in CD45 isoform expression on T cells with a loss of higher molecular weight isoforms and increased expression of lower molecular weight (CD45R0) isoform. This shift in CD45 isoform expression from CD45RBHi to CD45RBLo was associated with an increase in the intragraft expression of transcripts for interleukin (IL) 4 and IL-10, consistent with the expected activity of this distinct immunoregulatory T cell subset. Antibody-mediated targeting of CD45 may induce tolerance through novel mechanisms and have direct applicability to clinical transplantation in humans.

Differential signaling through the T cell receptor: from biochemistry to transplantation tolerance

Recent advances in our understanding of the structural nature of T cell activation and signal transduction from the T cell receptor for antigen make possible the development of new tolerogenic strategies. Here, we summarize the evidence supporting a critical role for the co-receptor molecule (CD4 or CD8) and CD45 in determining the pattern of T cell receptor-mediated signaling. The consequences of this differential signaling can range from T cell proliferation and cytokine production to the establishment of a state of proliferative unresponsiveness known as T cell anergy. Inducing T cell anergy can be an alternative approach for the establishment of transplantation tolerance.

Structure-function analysis of the integrin beta 7 subunit: identification of domains involved in adhesion to MAdCAM-1

Beta 7 integrins serve special roles in mucosal immunity. Alpha 4 beta 7-mediated adhesion to mucosal addressin cell adhesion molecule-1 (MAdCAM-1) directs lymphocyte homing to the gut, and alpha E beta 7 mediates binding of lymphocytes to E-cadherin on epithelial cells. Since alpha 4 beta 7 mediates adhesion to MAdCAM-1 but alpha 4 beta 1 does not, we used beta 7/beta 1 chimeras to directly assess the importance of specific regions of beta 7 in MAdCAM-1 binding. We found a region of beta 7 (residues 46-386) that accounts for specificity of alpha 4 beta 7 binding to MAdCAM-1. We also used human/mouse and human/rat chimeric beta 7 subunits to map epitopes recognized by fifteen anti-beta 7 mAbs. Six of seven Abs that block adhesion to MAdCAM-1 and E-cadherin (Fib 21, 22, 27, 30, 504; Act-1) mapped to amino acid residues 176-250. Residues 176-250 lie within the region of beta 7 that specifies MAdCAM-1 binding and also within a region that has a predicted structure homologous to the metal ion-dependent adhesion site (MIDAS) domains of the integrin subunits alpha L and alpha M. Three new Abs that recognize beta 7 in the presence of Mn2+, but not Ca2+, and promote adhesion to MAdCAM-1, mapped to amino acids 46-149. One blocking and five other Abs mapped to other regions (amino acids 387-725). We conclude that a MIDAS-like domain serves a critical role in beta 7 integrin-mediated adhesion.

Structure-function analysis of the integrin beta 7 subunit: identification of domains involved in adhesion to MAdCAM-1

Beta 7 integrins serve special roles in mucosal immunity. Alpha 4 beta 7-mediated adhesion to mucosal addressin cell adhesion molecule-1 (MAdCAM-1) directs lymphocyte homing to the gut, and alpha E beta 7 mediates binding of lymphocytes to E-cadherin on epithelial cells. Since alpha 4 beta 7 mediates adhesion to MAdCAM-1 but alpha 4 beta 1 does not, we used beta 7/beta 1 chimeras to directly assess the importance of specific regions of beta 7 in MAdCAM-1 binding. We found a region of beta 7 (residues 46-386) that accounts for specificity of alpha 4 beta 7 binding to MAdCAM-1. We also used human/mouse and human/rat chimeric beta 7 subunits to map epitopes recognized by fifteen anti-beta 7 mAbs. Six of seven Abs that block adhesion to MAdCAM-1 and E-cadherin (Fib 21, 22, 27, 30, 504; Act-1) mapped to amino acid residues 176-250. Residues 176-250 lie within the region of beta 7 that specifies MAdCAM-1 binding and also within a region that has a predicted structure homologous to the metal ion-dependent adhesion site (MIDAS) domains of the integrin subunits alpha L and alpha M. Three new Abs that recognize beta 7 in the presence of Mn2+, but not Ca2+, and promote adhesion to MAdCAM-1, mapped to amino acids 46-149. One blocking and five other Abs mapped to other regions (amino acids 387-725). We conclude that a MIDAS-like domain serves a critical role in beta 7 integrin-mediated adhesion.

Indefinite islet allograft survival in mice after a short course of treatment with anti-CD45 monoclonal antibodies

BACKGROUND

Although islet cell transplantation is considered an ideal form of endocrine replacement for type I diabetes, clinical application in humans is still not feasible. New immunosuppressive strategies are clearly needed to control inexorable rejection. CD45 is a family of transmembrane protein tyrosine phosphatases critically involved in the regulation of lymphocyte activation signals. Anti-CD45RB monoclonal antibody can prevent rejection of murine renal allografts.

METHODS

Here, we examine the consequences of targeting CD45 in murine islet cell transplantation. Diabetic mice recipients received islet allografts under the kidney capsule and were divided into seven groups. Recipients received no treatment (controls) or anti-CD45RB monoclonal antibody (mAb; MB23G2 or C363.16A) at different dosages and treatment intervals.

RESULTS

All untreated control animals lost islet function, becoming hyperglycemic within 10-17 days after transplantation. Animals treated with either anti-CD45RB mAb showed a significant prolongation of islet allograft survival when compared with controls. Anti-CD45RB MB23G2 at 100 microg/day, given on days -1, 0, and 5 was particularly effective, inducing indefinite islet allograft survival in 60% of recipients.

CONCLUSIONS

These results indicate that anti-CD45 mAbs are potent immunomodulatory agents, able to sustain indefinite islet allograft function after a short treatment course in the highly immunogenic model of islet transplantation.

Alpha 4 beta 7 integrin expression is associated with the leukemic evolution of human and murine T-cell lymphoblastic lymphomas

We have previously shown that the in vivo coordinated expression of individual alpha 4 and beta 7 integrin chains correlated with the leukemic potential displayed by cell lines derived from murine lymphoblastic T-cell lymphomas (T-LBLs) when transplanted subcutaneously into syngeneic AKR mice. In the present study, by using immunofluorescence and immunocytochemical analyses, we have confirmed that the in vivo up-regulation of the alpha 4 beta 7 heterodimeric complex is associated with the leukemic behavior of AKR T-LBLs. In addition, when compared with the parental, highly leukemic NQ22 cells, the variant cell line NQ22V exhibited a reduced leukemic potential that was invariably associated with a delayed alpha 4 beta 7 up-regulation in vivo Moreover, the leukemic cell line SJ-1, derived from a spontaneous T-LBL of the SJL strain, also displayed high levels of alpha 4 beta 7 expression with a pattern of tissue distribution similar to that of NQ22 cells from leukemic AKR animals. Of note, in most of the tissues involved by murine T-LBL dissemination, and particularly in liver, kidney, and lung, alpha 4 beta 7-positive leukemic cells were always located around strongly VCAM-1-positive vascular spaces. These findings are consistent with a possible role of alpha 4 beta 7/VCAM-1 interactions in the extravasation and, consequently, in the leukemic dissemination of murine T-LBL cells. Immunocytochemical analysis carried out in 11 human T-LBLs showed that pathological lymph nodes from all 7 cases with bone marrow infiltration at presentation carried alpha 4 beta 7-positive cells, whereas all 4 aleukemic T-LBLs were repeatedly alpha 4 beta 7 negative, also in metachronous lesions. These findings suggest that alpha 4 beta 7-positive human T-LBLs may represent a distinct clinicopathological entity. In addition, alpha 4 beta 7 expression was significantly more prevalent in younger patients (< 11 years; P = 0.02), further supporting such a hypothesis. Moreover, as in murine T-LBLs, the pattern of alpha 4 beta 7 positivity in involved lymph nodes was mainly focal, whereas nearly all neoplastic cells infiltrating bone marrow expressed this integrin, suggesting a possible role for alpha 4 beta 7 in the leukemic dissemination also of human T-LBLs.

Differential expression of tissue-specific adhesion molecules on human circulating antibody-forming cells after systemic, enteric, and nasal immunizations. A molecular basis for the compartmentalization of effector B cell responses

Expression of the adhesion molecules CD44, L-selectin (CD62L), and integrin alpha 4 beta 7 by antibody-secreting cells (ASC) was examined in human volunteers after oral, rectal, intranasal, or systemic immunization with cholera toxin B subunit. Almost all blood ASC, irrespective of immunization route, isotype (IgG and IgA), and immunogen, expressed CD44. On the other hand, marked differences were observed between systemically and intestinally induced ASC with respect to expression of integrin alpha 4 beta 7 and L-selectin, adhesion molecules conferring tissue specificity for mucosal tissues and peripheral lymph nodes, respectively. Thus, most ASC induced at systemic sites expressed L-selectin, whereas only a smaller proportion of ASC expressed alpha 4 beta 7. In contrast, virtually all IgA- and even IgG-ASC detected after peroral and rectal immunizations expressed alpha 4 beta 7, with only a minor fraction of these cells expressing L-selectin. Circulating ASC induced by intranasal immunization displayed a more promiscuous pattern of adhesion molecules, with a large majority of ASC coexpressing L-selectin and alpha 4 beta 7. These results demonstrate that circulating ASC induced by mucosal and systemic immunization express different sets of adhesion molecules. Furthermore, these findings provide for the first time evidence for differential expression of adhesion molecules on circulating ASC originating from different mucosal sites. Collectively, these results may explain the anatomical division of mucosal and systemic immune responses in humans as well as the compartmentalization of mucosal immune responses initiated in the upper vs. the lower aerodigestive tract.

Preferential expression of the mucosal homing receptor integrin alpha 4 beta 7 in gastrointestinal non-Hodgkin's lymphomas

Recent studies have identified the integrin alpha 4 beta 7 as a mucosal homing receptor that mediates lymphocyte migration to the intestinal mucosa by binding to MAdCAM-1, a vascular recognition molecule (addressin) selectively expressed on mucosal endothelium. In the present study, we have assessed the expression of alpha 4 beta 7 on B- and T-cell non-Hodgkin's lymphomas of different primary localization and on related normal lymphocytes. Among B-lineage lymphomas, expression of alpha 4 beta 7 was present in the majority of cases of malignant lymphomatous polyposis of the intestine and low-grade lymphoma of the mucosa-associated lymphoid tissue/monocytoid B-cell lymphoma and in some cases of precursor B-cell lymphoma. CLL/small lymphocytic lymphoma, (nodal) mantle cell lymphoma, follicular center cell lymphoma, Burkitt's lymphoma, and diffuse large B-cell lymphoma were virtually always alpha 4 beta 7 negative, as was the case when localized in the mucosa-associated lymphoid tissue. The normal B cells of the follicle mantles and part of the B cells of the extrafollicular B-cell compartment of lymphoid tissues expressed moderate levels of alpha 4 beta 7. By contrast, follicular center cells were alpha 4 beta 7 negative. Among T-lineage lymphomas, expression of alpha 4 beta 7 was also strongly related to the primary localization; in mucosal, nodal, and cutaneous T cell lymphomas the percentage of positive cases was 56%, 17%, and 0%, respectively. All cases of precursor T-cell lymphoma were alpha 4 beta 7 negative. High expression of alpha 4 beta 7 was found on a subset of peripheral blood memory T cells as well as on lymphocytes in the intestinal mucosa. We conclude that non-Hodgkin's lymphomas that are related to mucosa-associated B- and T-lymphocyte populations selectively express the mucosal homing receptor alpha 4 beta 7. The presence of this receptor underscores their distinctive character and may play an important role in determining their characteristic mucosal dissemination pattern.

Digestive tract involvement in Langerhans cell histiocytosis. The French Langerhans Cell Histiocytosis Study Group

BACKGROUND

Langerhans cell histiocytosis (LCH) is a rare disease with a wide clinical spectrum. Although little is known of gastrointestinal involvement in LCH, it may be a major clinical problem. We investigated clinical, pathologic, and immunohistochemical features of digestive tract LCH involvement in children.

PATIENTS

Selection criteria consisted of the presence of LCH with digestive symptoms, and histologic confirmation of gastrointestinal involvement. Seven children (2%) met the criteria among 348 cases of LCH in a French national retrospective survey from 1983 to 1993. Two children whose LCH was diagnosed in 1994 were also selected.

RESULTS

Nine children with LCH and digestive tract involvement were studied. Clinical features at presentation included skin (9/9) and mucosal (4/9) involvement, failure to thrive (5/9), diarrhea (7/9), bloody stools (4/7), vomiting (4/9), and hypoalbuminemia (8/9). Five of the nine children died; factors associated with a poor prognosis included young age, organ dysfunction (stage 4), and need for parenteral nutrition. Unlike control biopsy specimens, LCH cells of children with digestive tract involvement disclosed expression of the mucosal homing receptor integrin alpha 4 beta 7 on frozen skin and digestive tract biopsy specimens.

CONCLUSION

Cutaneous, mucosal, and digestive tract involvement in LCH is a clinicopathologic entity. The prognosis and treatment of LCH depend on the extent of the disease; therefore the treatment of these disseminated forms should not be delayed. Thus children with cutaneous LCH and digestive symptoms should undergo digestive tract biopsies. Studies of homing receptors may contribute to our understanding of the mechanisms of dissemination in LCH.

Expression of the beta 7 integrin by human endothelial cells

Integrin adhesion receptors mediate fundamental intercellular interactions of many cell types as well as cellular interactions with specific extracellular matrix molecules. To date, the beta 7 integrin has been shown to be expressed by leukocyte subsets and to mediate interactions of these cells with extracellular matrix molecules as well as with endothelial and epithelial cells. The data presented here indicate that human endothelial cells also express the beta 7 integrin both in vitro and in situ. Analysis of cDNA indicated that endothelial beta 7 was identical to that expressed by leukocytes. Cell surface expression of beta 7 was increased by exposure of the endothelium to the pro-inflammatory cytokines, tumor necrosis factor-alpha and interleukin-1 beta. In leukocytes, beta 7 complexes with alpha 4 or alpha E integrin chains. Endothelial cells also expressed a number of alpha-integrin chains, including alpha 4, but not alpha E. The expression and utilization of beta 7, presumably complexed with alpha 4, by endothelial cells may be instrumental in the maintenance of the function or phenotype of endothelial cells.

Distribution of beta 7 integrins in human intestinal mucosa and organized gut-associated lymphoid tissue

Two alternative integrins involved in mucosal homing (alpha 4 beta 7) or epithelial retention (alpha E beta 7) of lymphocytes were examined in the human gut. The distribution of the beta 7 subunit [monoclonal antibody (mAb) M301] was bimodal in that it was strongly expressed by alpha E beta 7 + cells but weakly by alpha 4 beta 7 + cells. More than 90% of intraepithelial lymphocytes (IEL), including the minor subsets of CD4+, T-cell receptor (TCR) gamma/delta +, and CD3- cells, expressed alpha E beta 7 as did most lamina propria CD8+ (88%) and a fraction (36%) of CD4+ lymphocytes. Conversely, B-lineage cells (CD19+) and macrophages (CD68+) were negative. In gut-associated lymphoid tissue (GALT: Peyer's patches and appendix) only a few (< 5%) cells were positive for alpha E beta 7 (confined to CD8+ lymphocytes and CD11c+ putative dendritic cells). A relatively small fraction of IEL (30-50%) expressed alpha 4 beta 7 (mAb Act-1), while most (70%) lamina propria T and B lymphocytes, blasts, plasma cells and macrophages were positive. In GALT, T lymphocytes expressed similar levels of alpha 4 beta 7 as in the lamina propria whereas relatively few B lymphocytes (< 50%) were positive. Isolated lamina propria CD8+, CD4+, CD19+, and CD38+ cells contained mRNA for alpha 4 and the former three subsets as well as appendix CD8+ cells also for beta 7 while only lamina propria CD8+ cells had mRNA for alpha E. Together, the results suggested that alpha E beta 7 and alpha 4 beta 7 are differentially regulated in inductive sites and effector sites of the human gut. Because lymphoid cells at both sites expressed mainly alpha 4 beta 7, this integrin may be a homing receptor on memory and effector cells bound for lamina propria as well as on naive lymphocytes extravasating in GALT. Conversely, because alpha E beta 7 was mainly expressed by CD8+ cells in epithelium and lamina propria, it was probably induced after extravasation, in agreement with the observation that IEL and a fraction of lamina propria T lymphocytes (mainly CD8+ cells) generally expressed higher levels of beta 7 than most CD4+ and B cells. Also a subset of putative dendritic cells located near the follicle-associated epithelium of GALT expressed alpha E beta 7, perhaps reflecting epithelial interaction during primary immune responses.

Specific regulation of VLA-4 and alpha 4 beta 7 integrin expression on human activated T lymphocytes

Modulation of VLA integrins was studied in several human T cell clones upon specific and nonspecific cellular activation. Human activated T lymphocytes down-regulated both alpha 4 beta 1 and alpha 4 beta 7 integrins upon specific recognition of alloantigens (cytotoxic T cells) or in the presence of Staphylococcus enterotoxin B (superantigen recognizing noncytotoxic T cells). In contrast, the expression of other membrane integrins, such as VLA-1 and VLA-5 integrins, was not modified. Down-regulation of alpha 4 beta 1 and alpha 4 beta 7 integrins was observed as early as 3 h after stimulation, lasted later than 72 h and was partially inhibited by cytochalasin D. Interestingly, neither target cells nor NK cells modulated CD49d expression after interaction with T cells of K562, respectively, suggesting that CD49d expression was linked to specific T cell activation. The down-regulation of the CD49d chain in T cell clones stimulated with immobilized anti-CD3 mAbs confirmed the role of TCR-mediated activation in CD49d regulation. However, the CD3-independent cellular aggregation induced by soluble anti-CD43 mAb was also able to strongly down-regulate alpha 4 beta 1 and alpha 4 beta 7. The present work shows the first evidence that CD49d subunit-bearing integrin expression is distinctly regulated from other integrins after Ag or superantigen recognition by human activated T cells. CD49d modulation may be relevant for the traffic and tissue localization of locally activated T cells during immune responses.

Specific regulation of VLA-4 and alpha 4 beta 7 integrin expression on human activated T lymphocytes

Modulation of VLA integrins was studied in several human T cell clones upon specific and nonspecific cellular activation. Human activated T lymphocytes down-regulated both alpha 4 beta 1 and alpha 4 beta 7 integrins upon specific recognition of alloantigens (cytotoxic T cells) or in the presence of Staphylococcus enterotoxin B (superantigen recognizing noncytotoxic T cells). In contrast, the expression of other membrane integrins, such as VLA-1 and VLA-5 integrins, was not modified. Down-regulation of alpha 4 beta 1 and alpha 4 beta 7 integrins was observed as early as 3 h after stimulation, lasted later than 72 h and was partially inhibited by cytochalasin D. Interestingly, neither target cells nor NK cells modulated CD49d expression after interaction with T cells of K562, respectively, suggesting that CD49d expression was linked to specific T cell activation. The down-regulation of the CD49d chain in T cell clones stimulated with immobilized anti-CD3 mAbs confirmed the role of TCR-mediated activation in CD49d regulation. However, the CD3-independent cellular aggregation induced by soluble anti-CD43 mAb was also able to strongly down-regulate alpha 4 beta 1 and alpha 4 beta 7. The present work shows the first evidence that CD49d subunit-bearing integrin expression is distinctly regulated from other integrins after Ag or superantigen recognition by human activated T cells. CD49d modulation may be relevant for the traffic and tissue localization of locally activated T cells during immune responses.

Prevention and reversal of renal allograft rejection by antibody against CD45RB

Rejection continues to be the single largest impediment to successful organ transplantation. Antilymphocyte globulin, which contains antibodies that react with the leukocyte common antigen known as CD45, has proved to be one of the most effective agents for preventing rejection. We have shown earlier that a monoclonal antibody directed against the RB isoform of CD45 substantially inhibits the alloreactivity of human CD4+ lymphocytes in vitro. Here we investigate whether CD45RB could be an appropriate target for preventing renal allograft rejection in mice. Mice treated with two injections of a monoclonal antibody (MB23G2) raised against CD45RB protein all survived and had normal renal function. Furthermore, this antibody reversed acute rejection when therapy was delayed until day 4, and the mice survived for their natural lifespan. The immunosuppression achieved may find application in the prevention and treatment of transplant rejection in man.

Stimulation of tyrosine phosphorylation after ligation of beta7 and beta1 integrins on human B cells

B lymphocytes express several members of the integrin family of adhesion molecules that mediate cell-cell and cell-extracellular matrix interactions. In addition to beta1 integrins, predominantly alpha4 beta1, mature B cells also express alpha4 beta7, which is a receptor for vascular cell adhesion molecule-1 and fibronectin, and is also involved in the homing of B cells to mucosal sites through binding to a third ligand, mucosal address in cell adhesion molecule-1. Here we describe that crosslinking of alpha4 beta7 integrins on B cell lines and normal tonsillar B cells, induces tyrosine phosphorylation of multiple substrates of 105-130 kD, indicating that beta7 integrin plays a role as signaling molecule in B cells. This pattern of phosphorylated proteins was very similar to that induced following ligation of alpha4 beta1. Interestingly, ligation of alpha5 beta1 or alpha6 beta1 also stimulated the 105-125 kD group of phosphorylated proteins, whereas ligation of beta2 integrins did not. The focal adhesion tyrosine kinase p125FAK was identified as one of these substrates. Beta1 or beta7 mediated tyrosine phosphorylations were markedly decreased when the microfilament assembly was inhibited by cytochalasin B. These results suggest that intracellular signals initiated by different integrins in B cells may converge, to similar cytoskeleton-dependent tyrosine phosphorylated proteins.

Human intestinal B-cell blasts and plasma cells express the mucosal homing receptor integrin alpha 4 beta 7

Interactions between homing receptors on circulating leucocytes and endothelial addressins regulate tissue-specific cellular extravasation. Although integrin alpha 4 beta 7 appears to be the main receptor for gut-homing T lymphocytes, less is known about molecules mediating mucosal B cell homing. Expression of integrin alpha 4 beta 7 on B lymphocytes, B cell blasts, and plasma cells in human gut-associated lymphoid tissue (GALT; the Peyer's patches and appendix) and lamina propria was studied by multi-colour immunofluorescence applied on cryosections. Isolated mononuclear cells from the same tissue compartments were examined by flow cytometry and compared with peripheral blood B cells. Integrin alpha 4 beta 7 was expressed by IgA+ B cell blasts and plasma cells (CD38high) in the lamina propria, B cell blasts in GALT, and sIgD+ B lymphocytes in peripheral blood. In contrast, GALT sIgD+ B lymphocytes were negative or only weakly positive for alpha 4 beta 7. These results suggested that B lymphocytes down-regulate alpha 4 beta 7 upon extravasation in GALT but up-regulate this integrin after antigen-priming. Thus, alpha 4 beta 7 may be a homing receptor also for B cell blasts extravasating in the gut lamina propria, where this integrin is maintained on plasma cells, perhaps as a local retention factor.

Effects of monoclonal antibody against CD45RB on peripheral blood mononuclear cell proliferation and on HLA-DR and adhesion molecule expression on thyrocytes of patients with autoimmune thyroid disease

To evaluate the role of CD45 (especially that of the ectodomain region B) on immunocyte-thyrocyte signaling in patients with autoimmune thyroid disease (AITD), we have examined the in vitro and in vivo effects of a monoclonal antibody (mAb) against with CD45RB, termed MT3. MT3 was added to cultured peripheral blood mononuclear cells (PBMC) from patients with AITD and was additionally injected into severe combined immunodeficient (SCID) mice to which Graves' thyroid cells and intrathyroidal lymphocytes were engrafted. MT3 stimulated proliferation of PBMC when cultured for 2 to 3 days in patients with Hashimoto's thyroiditis (HT) and Graves' disease (GD) and in normal controls (NC). However, when cultured for 7 days, the stimulation index [SI: counts per minute (cpm) with mAb/cpm without mAb] was lowered by MT3 in NC and GD patients. However, the mean SI was not lowered in patients with HT. In SCID mice, the concentrations of human immunoglobulin G, antithyroglobulin and antithyroperoxidase antibodies in sera were not significantly changed by injecting MT3. The expression of human leukocyte antigen (HLA)-DR and intercellular adhesion molecule (ICAM)-1 on engrafted human thyrocytes decreased after the tissues were engrafted into the control mice to which vehicle alone was injected. However, in the mice injected with MT3, HLA-DR and ICAM-1 expression remained high or up-regulated by the injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibody ligation of CD7 leads to association with phosphoinositide 3-kinase and phosphatidylinositol 3,4,5-trisphosphate formation in T lymphocytes

The CD7 40-kDa glycoprotein is present on a major subset of human T cells and in the presence of phorbol esters mediates an accessory pathway of T cell activation. Hitherto, the intracellular events elicited by CD7 have been ill-defined. This report demonstrates that cross-linking of CD7 results in the formation of phosphatidic acid in the absence of phosphatidylinositol-4,5-bisphosphate metabolism and also the formation of D-3 phosphoinositides lipids which have been postulated to act as intracellular regulatory molecules. The magnitude of D-3 phosphoinositide formation was similar to that induced by CD3. Both the CD7- and CD3-induced elevation of phosphatidylinositol 3,4,5-trisphosphate approximately 5-10 fold less than that elicited by ligation of the costimulatory molecule CD28 by its counter receptor CD80. The formation of D-3 phosphoinositides following ligation of CD7 coincided with the co-association of CD7 with phosphoinositide 3-kinase, the enzyme which mediates the formation of D-3 phosphoinositide lipids. In contrast, ligation of another reported T cell accessory molecule CD5, failed to elicit formation of D-3 phosphoinositides, implying that phosphoinositide 3-kinase is not coupled to all T cell molecules with accessory functions. Since D-3 phosphoinositides have been suggested to play a pivotal role in T cell costimulatory signals induced by CD28, the results presented in this study suggest that CD7 may also influence T cell activation via this pathway.

Anti-B cell antibodies for the treatment of monoclonal Epstein-Barr virus-induced lymphoproliferative syndrome after multivisceral transplantation

Epstein-Barr virus-induced lymphoproliferative syndrome (EBV-LPS) is associated with OKT3 therapy in transplant patients. Response to chemotherapy or radiation is generally poor, while polyclonal EBV-LPS has had favorable responses to therapy with CD21 and CD24 monoclonal antibodies. Oligoclonal disease has not been previously reported to respond to therapy with CD21 and CD24. We report a 27-y old woman who developed a monoclonal EBV-LPS (confirmed by southern analysis of tumour for EBV DNA) after 180 mg of OKT3 for a multivisceral transplant. The patient achieved clinical remission for more than 2 months, but later died from cytomegalovirus pneumonia. Levels of CD21 and CD24 were > 2000 ng/ml during therapy and no human anti-mouse antibodies were formed. Peripheral blood B cells were cleared during therapy. We conclude that CD21 and CD24 monoclonal antibodies may be of value in the therapy of oigoclonal EBV-LPS, and merit further study.

Integrin alpha 4 beta 7 co-stimulation of human peripheral blood T cell proliferation

The integrin alpha 4 beta 7 mediates lymphocytes adhesion to VCAM-1 on activated endothelium, fibronectin in the extracellular matrix, and the mucosal vascular addressin MAdCAM-1. It is unclear whether alpha 4 beta 7 performs any function beyond directing specific adhesion reactions. We addressed the possibility that triggering of alpha 4 beta 7 with a specific monoclonal antibody was capable of delivering an accessory stimulus that would coactivate T cells and lead to proliferation. At submitogenic levels of anti-CD3 stimulation, triggering of alpha 4 beta 7 by immobilized mAb ACT-1 resulted in T cell blastogenesis, IL-2 production, expression of the IL-2 receptor alpha chain CD25, and ultimately DNA synthesis. These results indicate that the integrin alpha 4 beta 7 is involved in more than lymphocyte adhesion and homing but also plays a role in cell signaling.

CD7 is associated with CD3 and CD45 on human T cells

The CD7 cluster of mAb identifies a 40-kDa glycopolypeptide that is present on a major subset of human T cells. CD7 Ag mediates an accessory pathway of T cell activation in that cross-linked CD7 mAb are mitogenic, and signals delivered via CD7 Ag stimulate integrin-mediated adhesion. We have found that the CD7 molecule is associated with a tyrosine kinase whose major substrate is CD45. In vitro phosphorylation of CD7, CD3, or CD45 immunoprecipitates prepared from lysates of human T cells showed a similar pattern of multiple phosphorylated polypeptides; in addition, these immunoprecipitates phosphorylated a tyrosine kinase-specific peptide. Surface-iodinated T cells were lysed and immunoprecipitated with CD7, CD3, and CD45 mAb. Bands characteristic of CD45 and CD3 were identified in CD7 immunoprecipitates. Confirmation of an association of CD7 with CD3 and CD45 was obtained from Western blotting and fluorescence resonance energy transfer experiments. Furthermore, we provide evidence using immunoprecipitation and Western blotting that CD7 exists as a homodimer. These data support the hypothesis that CD7 exists in an oligomeric complex with CD3/TCR, the protein tyrosine phosphatase CD45, and a tyrosine kinase, thereby providing a physical basis for the accessory role of the CD7 molecule in T cell activation.

CD7 is associated with CD3 and CD45 on human T cells

The CD7 cluster of mAb identifies a 40-kDa glycopolypeptide that is present on a major subset of human T cells. CD7 Ag mediates an accessory pathway of T cell activation in that cross-linked CD7 mAb are mitogenic, and signals delivered via CD7 Ag stimulate integrin-mediated adhesion. We have found that the CD7 molecule is associated with a tyrosine kinase whose major substrate is CD45. In vitro phosphorylation of CD7, CD3, or CD45 immunoprecipitates prepared from lysates of human T cells showed a similar pattern of multiple phosphorylated polypeptides; in addition, these immunoprecipitates phosphorylated a tyrosine kinase-specific peptide. Surface-iodinated T cells were lysed and immunoprecipitated with CD7, CD3, and CD45 mAb. Bands characteristic of CD45 and CD3 were identified in CD7 immunoprecipitates. Confirmation of an association of CD7 with CD3 and CD45 was obtained from Western blotting and fluorescence resonance energy transfer experiments. Furthermore, we provide evidence using immunoprecipitation and Western blotting that CD7 exists as a homodimer. These data support the hypothesis that CD7 exists in an oligomeric complex with CD3/TCR, the protein tyrosine phosphatase CD45, and a tyrosine kinase, thereby providing a physical basis for the accessory role of the CD7 molecule in T cell activation.

Expression of the mucosal homing receptor alpha 4 beta 7 in malignant lymphomatous polyposis of the intestine

Recent studies have identified the integrin alpha 4 beta 7 as a mucosal homing receptor that mediates lymphocyte migration to the intestinal mucosa by binding to MAd-CAM-1, which is a vascular recognition molecule (adressin) selectively expressed on mucosal endothelium. The expression of the alpha 4 beta 7 mucosal homing receptor was studied in eight cases of malignant lymphomatous polyposis (MLP). This unusual presentation of non-Hodgkin's lymphoma of mantle cell type is characterized by multifocal lymphomatous involvement of the gastrointestinal tract. Unlike nodal mantle cell lymphomas, cases of MLP showed expression of alpha 4 beta 7, suggesting that this homing receptor plays an important role in determining the characteristic mucosal dissemination pattern of MLP.

Expression and function of the MAdCAM-1 receptor, integrin alpha 4 beta 7, on human leukocytes

Recirculation of mouse lymphocytes to the gut involves binding of the lymphocyte integrin alpha 4 beta 7 to the mucosal vascular addressin, MAdCAM-1. In humans, indirect evidence suggests that CD4+ T cells that express high levels of alpha 4 beta 7 migrate selectively to the gut. We now report that human adult blood CD8+ T cells and B cells, like CD4+ T cells, have heterogeneous expression of alpha 4 beta 7. In contrast, NK cells, eosinophils, and newborn blood T and B cells have relatively homogeneous expression of alpha 4 beta 7. CD4+ and CD8+ T cell expression of alpha 4 beta 7 was related to age, CD45RA expression, and integrin beta 1 (CD29) expression, suggesting that alpha 4 beta 7 expression changes after primary activation of CD4+ and CD8+ T cells in vivo. To directly determine whether human alpha 4 beta 7 mediates adhesion to MAdCAM-1, we performed in vitro adhesion assays with two alpha 4 beta 7+ human lymphoma cell lines. The results indicate that human alpha 4 beta 7 is a receptor for MAdCAM-1, whereas alpha 4 beta 1 is not. Adhesion of HUT 78 cells to MAdCAM-1 required Mn2+, whereas adhesion of RPMI 8866 cells did not, suggesting that alpha 4 beta 7 may have at least two distinct functional states. The ability of lymphocytes to bind to MAdCAM-1 and recirculate to mucosal organs is likely to be influenced both by the level of alpha 4 beta 7 expression and by the functional state of the alpha 4 beta 7 molecule.

Expression and function of the MAdCAM-1 receptor, integrin alpha 4 beta 7, on human leukocytes

Recirculation of mouse lymphocytes to the gut involves binding of the lymphocyte integrin alpha 4 beta 7 to the mucosal vascular addressin, MAdCAM-1. In humans, indirect evidence suggests that CD4+ T cells that express high levels of alpha 4 beta 7 migrate selectively to the gut. We now report that human adult blood CD8+ T cells and B cells, like CD4+ T cells, have heterogeneous expression of alpha 4 beta 7. In contrast, NK cells, eosinophils, and newborn blood T and B cells have relatively homogeneous expression of alpha 4 beta 7. CD4+ and CD8+ T cell expression of alpha 4 beta 7 was related to age, CD45RA expression, and integrin beta 1 (CD29) expression, suggesting that alpha 4 beta 7 expression changes after primary activation of CD4+ and CD8+ T cells in vivo. To directly determine whether human alpha 4 beta 7 mediates adhesion to MAdCAM-1, we performed in vitro adhesion assays with two alpha 4 beta 7+ human lymphoma cell lines. The results indicate that human alpha 4 beta 7 is a receptor for MAdCAM-1, whereas alpha 4 beta 1 is not. Adhesion of HUT 78 cells to MAdCAM-1 required Mn2+, whereas adhesion of RPMI 8866 cells did not, suggesting that alpha 4 beta 7 may have at least two distinct functional states. The ability of lymphocytes to bind to MAdCAM-1 and recirculate to mucosal organs is likely to be influenced both by the level of alpha 4 beta 7 expression and by the functional state of the alpha 4 beta 7 molecule.

Identification of a combinatorial epitope expressed by the integrin alpha 4 beta 1 heterodimer involved in the regulation of cell adhesion

The alpha 4 integrin subunit can associate with either the beta 1- or beta 7-integrin subunit to form two unique adhesion receptors alpha 4 beta 1 and alpha 4 beta 7. We developed a monoclonal antibody (mAb 19H8) that immunoprecipitated alpha 4 beta 1, induced homotypic leukocyte aggregation, and blocked the binding of cells to a synthetic peptide corresponding to the CS-1 peptide region of fibronectin. Aggregation cross-blocking analysis suggested that mAb 19H8 belonged to the group of mAbs that react with the B2 epitope of the alpha 4 subunit (alpha 4.B2 epitope); however, unlike the alpha 4.B2-specific mAb L25, mAb 19H8 did not immunoprecipitate alpha 4 beta 7. In addition, mAb 19H8 did not bind to beta 1-positive cells unless transfected with alpha 4 cDNA. These results indicated that mAb 19H8 was not specific for an individual alpha 4, beta 1, or beta 7 subunit but reacted with an epitope formed from the association of alpha 4 with beta 1. Separating the alpha 4 from the beta 1 subunit, by removing divalent cations or by treatment with high pH, disrupted mAb 19H8 binding. In contrast, the alpha 4-specific mAb L25 and the beta 1-specific mAb 18D3 could react with their respective subunits without subunit association. Therefore, mAb 19H8 defined a novel regulatory epitope expressed by the integrin alpha 4 beta 1.

Analysis of peripheral blood lymphocyte populations and immune function from children exposed to cyclosporine or to azathioprine in utero

We have analyzed PBL from 7 children exposed to CsA in utero and 4 children exposed to AZA in utero. Expression of CD3, CD4, CD8, and CD20 were normal for both groups of children; however, significant differences were detected in the expression of CD45RA, CD45R0, and CD29. While CsA-exposed children had higher density of CD45RA, and a higher proportion of CD45RA+R0- T cells, than did unexposed children, those exposed to AZA alone had decreased CD45RA+ and a large increase in CD45RA-R0+ T cells. It appears the exposure to CsA slightly delays T cell development, whereas exposure to AZA, without concomitant exposure to CsA, accelerates development to that of an adult. The effects of CsA abrogated the effects of AZA when both were present during pregnancy. The expression of CD29, the beta 1-integrin, on T cells has been linked to enhanced ability to respond to recall antigens and to home to sites of infection. Among children exposed to CsA, T cells from cord blood and a 5-month-old infant have a normal CD29 profile. However from 1 to 6 years of age the proportion of T cells expressing a high density of CD29 is significantly lower (4-fold) than that of T cells from unexposed children. Because these children have no outward signs of immunodeficiency, we postulate that this low proportion is still sufficient for normal immune responsiveness. The distribution of CD29 on T cells was different for the 3 study groups. Among CsA-exposed children, although the proportion of CD29hi T cells was much reduced, all were CD45RA+, as was also the case for unexposed children. In contrast, among children exposed only to AZA, the majority of CD29hi T cells were CD45R0+. Serological testing indicated that immunoglobulin and complement levels, as well as seroconversion in response to vaccination, were normal among CsA-exposed children, with no detectable autoantibodies to cellular or tissue components, including parietal cells. Unlike T cell development in inbred rodents, the immune system in humans appears to be remarkably resilient, and successfully adapts to the presence of CsA during its early developmental stages. This work suggests that the presence of CsA throughout pregnancy has only a minimal effect on fetal immune development and appears to have less impact on T cells than does exposure to AZA only. We conclude that children exposed to CsA in utero are not likely to be at risk of immunodeficiency or autoimmunity.

Differential expression in rheumatoid synovium and synovial fluid of alpha 4 beta 7 integrin. A novel receptor for fibronectin and vascular cell adhesion molecule-1

T lymphocyte adhesion to vascular endothelium plays an important role in the immunopathogenesis of rheumatoid arthritis. The migration of T lymphocytes into the synovium is mediated by a variety of adhesion molecules, notably the integrins. We have prepared Act I, a murine mAb that identifies a novel integrin termed alpha 4 beta 7. The natural ligands for alpha 4 beta 7 are vascular cell adhesion molecule-1 and fibronectin; both molecules are up-regulated in the rheumatoid synovium. We investigated the expression of alpha 4 beta 7 in the three compartments of rheumatoid arthritis, the peripheral blood, synovial fluid, and synovial membrane, utilizing the FACS and immunoperoxidase microscopy of frozen tissues. The results of our experiments show a striking differential expression of alpha 4 beta 7 integrin in rheumatoid arthritis. Sixty-two percent of synovial membrane T cells expressed high density alpha 4 beta 7, in contrast to only 4.7% of synovial fluid and 9.1% of PBL. These data suggest that the expression of alpha 4 beta 7 integrin may provide a mechanism whereby certain T cells adhere to rheumatoid synovium while others remain in the synovial fluid. The augmented expression of alpha 4 beta 7 in the synovial membrane T cells may contribute to the development and perpetuation of rheumatoid arthritis.

Differential expression in rheumatoid synovium and synovial fluid of alpha 4 beta 7 integrin. A novel receptor for fibronectin and vascular cell adhesion molecule-1

T lymphocyte adhesion to vascular endothelium plays an important role in the immunopathogenesis of rheumatoid arthritis. The migration of T lymphocytes into the synovium is mediated by a variety of adhesion molecules, notably the integrins. We have prepared Act I, a murine mAb that identifies a novel integrin termed alpha 4 beta 7. The natural ligands for alpha 4 beta 7 are vascular cell adhesion molecule-1 and fibronectin; both molecules are up-regulated in the rheumatoid synovium. We investigated the expression of alpha 4 beta 7 in the three compartments of rheumatoid arthritis, the peripheral blood, synovial fluid, and synovial membrane, utilizing the FACS and immunoperoxidase microscopy of frozen tissues. The results of our experiments show a striking differential expression of alpha 4 beta 7 integrin in rheumatoid arthritis. Sixty-two percent of synovial membrane T cells expressed high density alpha 4 beta 7, in contrast to only 4.7% of synovial fluid and 9.1% of PBL. These data suggest that the expression of alpha 4 beta 7 integrin may provide a mechanism whereby certain T cells adhere to rheumatoid synovium while others remain in the synovial fluid. The augmented expression of alpha 4 beta 7 in the synovial membrane T cells may contribute to the development and perpetuation of rheumatoid arthritis.

Alpha 4 beta 7 integrin mediates B cell binding to fibronectin and vascular cell adhesion molecule-1. Expression and function of alpha 4 integrins on human B lymphocytes

Cell-cell and cell-extracellular matrix interactions are mediated by a wide array of cell surface molecules known as adhesion receptors, including the integrin family that comprises numerous alpha beta heterodimers. A new integrin group, the beta 7 subfamily, has been recently defined. Its two members, alpha 4 beta 7 and alpha H beta 7, are involved in the lymphocyte migration to the Peyer's patches and the intestinal mucosa, respectively. We have analyzed the expression of alpha 4 beta 7 integrin on B cells from different cellular compartments and at different activation states. Resting peripheral blood B lymphocytes constitutively express large amounts of alpha 4 beta 7. By contrast, alpha 4 beta 7 integrin, which is absent on resident B cells from different lymphoid tissues, is induced upon activation. Functional studies indicates that alpha 4 beta 7 is mediating B cell attachment to fibronectin and vascular cell adhesion molecule-1 through distinct epitopes on this integrin. Furthermore, the alpha 4 beta 7 integrin is also implicated in intercellular interactions as deduced by the ability of anti-alpha 4 beta 7 mAb to trigger homotypic B cell aggregation. Finally, alpha 4 beta 7 and alpha 4 beta 1 integrins redistribute at the cell membrane in a similar clustering pattern when B cells attach to fibronectin- and vascular cell adhesion molecule-1-coated surfaces. Our studies demonstrate the differential regulation on the expression and function of alpha 4 beta 7 integrin among different human B cell populations.

Alpha 4 beta 7 integrin mediates B cell binding to fibronectin and vascular cell adhesion molecule-1. Expression and function of alpha 4 integrins on human B lymphocytes

Cell-cell and cell-extracellular matrix interactions are mediated by a wide array of cell surface molecules known as adhesion receptors, including the integrin family that comprises numerous alpha beta heterodimers. A new integrin group, the beta 7 subfamily, has been recently defined. Its two members, alpha 4 beta 7 and alpha H beta 7, are involved in the lymphocyte migration to the Peyer's patches and the intestinal mucosa, respectively. We have analyzed the expression of alpha 4 beta 7 integrin on B cells from different cellular compartments and at different activation states. Resting peripheral blood B lymphocytes constitutively express large amounts of alpha 4 beta 7. By contrast, alpha 4 beta 7 integrin, which is absent on resident B cells from different lymphoid tissues, is induced upon activation. Functional studies indicates that alpha 4 beta 7 is mediating B cell attachment to fibronectin and vascular cell adhesion molecule-1 through distinct epitopes on this integrin. Furthermore, the alpha 4 beta 7 integrin is also implicated in intercellular interactions as deduced by the ability of anti-alpha 4 beta 7 mAb to trigger homotypic B cell aggregation. Finally, alpha 4 beta 7 and alpha 4 beta 1 integrins redistribute at the cell membrane in a similar clustering pattern when B cells attach to fibronectin- and vascular cell adhesion molecule-1-coated surfaces. Our studies demonstrate the differential regulation on the expression and function of alpha 4 beta 7 integrin among different human B cell populations.

Selective expression of integrin alpha 4 beta 7 on a subset of human CD4+ memory T cells with Hallmarks of gut-trophism

Human memory CD4+ T lymphocytes are heterogenous in expression of integrins; one subset has the unexpected phenotype beta 1 low alpha 4 high. We demonstrate that this subset is unique among CD4+ cells in expression of high levels of alpha 4 beta 7, detected by a distinctive mAb Act-1. alpha 4 beta 7 is involved in binding to both fibronectin and vascular cell adhesion molecule-1; Act-1 blocks cell binding to the former and augments binding to the latter. Act-1 expression marks a subset of memory cells that, unlike the predominant circulating memory cell, has up-regulated beta 7 rather than beta 1. Their phenotype is distinct from that described for skin-homing T cells and is fully consistent with that described for gut-homing T cells. Differential adhesion capacity of this subset is verified by selective binding to FN and vascular cell adhesion molecule-1 in a beta 1-independent fashion. Thus, alpha 4 beta 7 detected on this subset of circulating normal T cells fits the expectations for a gut-homing receptor.

Selective expression of integrin alpha 4 beta 7 on a subset of human CD4+ memory T cells with Hallmarks of gut-trophism

Human memory CD4+ T lymphocytes are heterogenous in expression of integrins; one subset has the unexpected phenotype beta 1 low alpha 4 high. We demonstrate that this subset is unique among CD4+ cells in expression of high levels of alpha 4 beta 7, detected by a distinctive mAb Act-1. alpha 4 beta 7 is involved in binding to both fibronectin and vascular cell adhesion molecule-1; Act-1 blocks cell binding to the former and augments binding to the latter. Act-1 expression marks a subset of memory cells that, unlike the predominant circulating memory cell, has up-regulated beta 7 rather than beta 1. Their phenotype is distinct from that described for skin-homing T cells and is fully consistent with that described for gut-homing T cells. Differential adhesion capacity of this subset is verified by selective binding to FN and vascular cell adhesion molecule-1 in a beta 1-independent fashion. Thus, alpha 4 beta 7 detected on this subset of circulating normal T cells fits the expectations for a gut-homing receptor.

Human mouse chimeric CD7 monoclonal antibody (SDZCHH380) for the prophylaxis of kidney transplant rejection

mAb directed against CD7 have been shown to inhibit T cell proliferation in the allogeneic mixed lymphocyte reaction suggesting that CD7 may be an appropriate target for in vivo immunotherapy. We performed a prospective randomized clinical trial with a human-mouse chimeric CD7 mAb (SDZCHH380) and compared it with murine OKT3 for the prophylaxis of kidney transplant rejection. Twenty recipients of first cadaveric renal allografts were randomized to receive either SDZCHH380 or OKT3. SDZCHH380 was well tolerated. Rejection was delayed to day 35. No patients were sensitized to SDZCHH380. In contrast 7/10 OKT3 patients made anti-OKT3 antibodies. SDZCHH380 coated peripheral blood and lymph node T cells and, in contrast to OKT3, induced minimal release of IL-2, IL-6, TNF-alpha, and IFN-gamma. In addition, we showed that CD7-negative T cells mediated rejection in one of the SDZCHH380-treated patients. We conclude that the human-mouse chimeric CD7 mAb SDZCHH380 is well tolerated, is not immunogenic, and merits further study in the prophylaxis of transplant rejection.

Human mouse chimeric CD7 monoclonal antibody (SDZCHH380) for the prophylaxis of kidney transplant rejection

mAb directed against CD7 have been shown to inhibit T cell proliferation in the allogeneic mixed lymphocyte reaction suggesting that CD7 may be an appropriate target for in vivo immunotherapy. We performed a prospective randomized clinical trial with a human-mouse chimeric CD7 mAb (SDZCHH380) and compared it with murine OKT3 for the prophylaxis of kidney transplant rejection. Twenty recipients of first cadaveric renal allografts were randomized to receive either SDZCHH380 or OKT3. SDZCHH380 was well tolerated. Rejection was delayed to day 35. No patients were sensitized to SDZCHH380. In contrast 7/10 OKT3 patients made anti-OKT3 antibodies. SDZCHH380 coated peripheral blood and lymph node T cells and, in contrast to OKT3, induced minimal release of IL-2, IL-6, TNF-alpha, and IFN-gamma. In addition, we showed that CD7-negative T cells mediated rejection in one of the SDZCHH380-treated patients. We conclude that the human-mouse chimeric CD7 mAb SDZCHH380 is well tolerated, is not immunogenic, and merits further study in the prophylaxis of transplant rejection.

Physical association of CD5 and the T cell receptor/CD3 antigen complex on the surface of human T lymphocytes

The physical association of CD5 and the T cell antigen receptor (TcR)/CD3 complex on the surface of intact human lymphocytes was investigated using co-capping experiments and fluorescence resonance energy transfer (FRET) analyses. Antibody-induced capping of CD5 or CD3 and double indirect immunofluorescence labeling revealed a specific co-localization of a significant fraction of CD3 and CD5 molecules on the T cell surface. By means of FRET measurements we studied further the physical proximity of CD5 and the TcR/CD3 complex at the surface of normal lymphocytes. Significant fluorescence energy transfer was measured between CD5 and CD3 molecules indicating that the associated molecules were within 10 nm of one another. No energy transfer was observed between the integrin alpha 4 beta 7 and CD3 or CD5. The close physical proximity measured between CD5 and CD3 correlates with our co-capping data and taken together the results show that the association of CD5 and the TcR/CD3 complex first detected by immunoprecipitation occurs on the surface of human T cells under physiologically relevant conditions.