The T cell receptor

Heat shock protein induced TCR γδ gene rearrangements in patients with oral cancer

We analyzed the T cell receptor (TCR) gammadelta gene repertoire in peripheral blood and tumor compartment of oral cancer (OC) patients before and after stimulation with heat shock proteins (hsp), which are known ligands for gammadelta T cells. Clonal TCR gamma and delta gene rearrangements in lymphocytes from tumor compartment and peripheral blood were studied using TCR Vgamma and Vdelta gene primers in PCR followed by heteroduplex analysis. Vgamma gene segments derived from VgammaI or VgammaII gene families were most dominantly expressed in peripheral blood lymphocytes (PBL) as compared to tumor infiltrating lymphocytes (TIL) of OC patients. Of the rearranged TCR delta alleles Vdelta1-Jdelta1 and Vdelta2-Jdelta1 gene rearrangements were the most predominant in PBL and TIL of OC patients respectively. Stimulation of gammadelta T cells with hsp 60/70 demonstrated a selective clonal expansion of Vgamma9-Vdelta2 (VgammaII family) subset indicating that, this expanded population of cells could be responsible for eliciting an immune response against oral tumor cells.

Positive and negative selection of T cell repertoires during differentiation in allogeneic bone marrow chimeras

T cells acquire immune functions during expansion and differentiation in the thymus. Mature T cells respond to peptide antigens (Ag) derived from foreign proteins when these peptide Ag are presented on the self major histocompatibility complex (MHC) molecules but not on allo-MHC. This is termed self-MHC restriction. On the other hand, T cells do not induce aggressive responses to self Ag (self-tolerance). Self-MHC restriction and self-tolerance are not genetically determined but acquired a posteriori by positive and negative selection in the thymus in harmony with the functional maturation. Allogeneic bone marrow (BM) chimera systems have been a useful strategy to elucidate mechanisms underlying positive and negative selection. In this communication, the contribution of BM chimera systems to the investigation of the world of T-ology is discussed.

Ocular transfer of retinal glial cells transduced ex vivo with adenovirus expressing viral IL-10 or CTLA4-Ig inhibits experimental autoimmune uveoretinitis

Gene transfer using immunomodulatory molecules is a promising tool for in vivo regulation of immune responses. Experimental autoimmune uveitis (EAU), which serves as a model for human ocular inflammation, is induced by systemic immunization with autoantigens, but its expression is restricted to the eye. Previously, we reported protection of rodents against EAU by intravenous or/and periocular injection of vIL-10-expressing adenovirus. Here, the expression of vIL-10 was targeted into the rat Lewis eye, by intravitreal injection of either the free virus or ex vivo transfected retinal Müller glial cells (RMG-vIL-10). As shown using GFP-expressing adenovirus, a longer expression of transgene was observed in the eye after transfer of transfected syngeneic RMG cells than was seen after injection of free virus. Intravitreal injection of RMG-vIL-10 led to significant decrease in ocular pathological manifestations, compared to control RMG cells. This was observed when cells were injected simultaneously with autoantigen, but also after a delayed administration of transfected cells. Finally, injection of RMG cells transfected with adenovirus expressing CTLA4 had a strongly protective effect. In conclusion, inhibition of antigen presentation at the site of expression of the autoimmune disorders represents an attractive alternative to treat ocular inflammation, and the transfer of ex vivo genetically modified cells provides a promising method to target the factor of interest into the eye.

Three-dimensional structural location and molecular functional effects of missense SNPs in the T cell receptor V? domain

The mechanisms by which human single nucleotide polymorphisms (SNPs) influence susceptibility to disease are not yet well understood. In a previous study, we developed a structure-based model that may be used to identify which missense SNPs are neutral and which are deleterious to protein function and so potentially involved in disease (Wang and Moult, Hum Mutat 2001;263-270). The model has now been applied to a set of 54 missense cSNPs in the 46 functional T-cell receptor Vbeta-genes. Most of these missense cSNPs are found to be neutral, but 10 are identified as likely deleterious to protein function. Only one was previously associated with disease. We suggest that the others may be disease related but that redundancy in the T-cell response prevents any simple, monogenic effect. Therefore, these SNPs are the most likely contributors to complex, polygenic disease traits. It has been noted that there is a surprisingly high (74%) fraction of nonsynonymous SNPs in these genes. Contrary to expectation, the analysis shows that these are not associated with an unusually high fraction of deleterious SNPs, nor do they significantly contribute to a larger range of antigen recognition or a reduced superantigen-binding repertoire.

Systematic identification of regulatory proteins critical for T-cell activation

BACKGROUND

The activation of T cells, mediated by the T-cell receptor (TCR), activates a battery of specific membrane-associated, cytosolic and nuclear proteins. Identifying the signaling proteins downstream of TCR activation will help us to understand the regulation of immune responses and will contribute to developing therapeutic agents that target immune regulation.

RESULTS

In an effort to identify novel signaling molecules specific for T-cell activation we undertook a large-scale dominant effector genetic screen using retroviral technology. We cloned and characterized 33 distinct genes from over 2,800 clones obtained in a screen of 7 x 108 Jurkat T cells on the basis of a reduction in TCR-activation-induced CD69 expression after expressing retrovirally derived cDNA libraries. We identified known signaling molecules such as Lck, ZAP70, Syk, PLC gamma 1 and SHP-1 (PTP1C) as truncation mutants with dominant-negative or constitutively active functions. We also discovered molecules not previously known to have functions in this pathway, including a novel protein with a RING domain (found in a class of ubiquitin ligases; we call this protein TRAC-1), transmembrane molecules (EDG1, IL-10R alpha and integrin alpha2), cytoplasmic enzymes and adaptors (PAK2, A-Raf-1, TCPTP, Grb7, SH2-B and GG2-1), and cytoskeletal molecules (moesin and vimentin). Furthermore, using truncated Lck, PLC gamma 1, EDG1 and PAK2 mutants as examples, we showed that these dominant immune-regulatory molecules interfere with IL-2 production in human primary lymphocytes.

CONCLUSIONS

This study identified important signal regulators in T-cell activation. It also demonstrated a highly efficient strategy for discovering many components of signal transduction pathways and validating them in physiological settings.

T-cell receptor V? gene usage by T cells reactive with the tumor-rejection antigen SART-1 in oral squamous cell carcinoma

We recently described that the SART-1(690-698) peptide could induce HLA-A24-restricted cytotoxic T lymphocytes (CTLs), which recognize the SART-1(259) (+) tumor cells from peripheral blood mononuclear cells (PBMCs) of HLA-A24(+) cancer patients. In our study, in 5 of 14 HLA-A24(+) patients with oral squamous cell carcinomas (SCCs), CTLs could be induced with the SART-1(690-698) peptide from the PBMCs. In 2 of the patients from whom the highest CTL activities were induced, the T-cell receptor (TCR) Vbeta repertoire expressed by the SART-1(690-698)-specific CTLs was found to be restricted and multiple Vbeta families were predominantly expressed in each patient. Although the predominant Vbeta families were different between the 2 patients, Vbeta7 was highly and commonly predominant. The same predominant Vbeta families were also detected in the tumor-infiltrating lymphocytes (TILs) from each patient, and each Vbeta family contained one or more unique T-cell clonotypes. The unique T-cell clonotypes were found to be common between the TILs and SART-1(690-698)-specific CTLs from each patient, and especially 2 T-cell clonotypes with Vbeta7 were identical even in the 2 patients. One of the 2 T-cell clonotypes with Vbeta7 was detected in the TILs from 11 of 14 HLA-A24(+) patients and another was found in those from 8 of HLA-A24(+) patients, while none of 10 HLA-A24(-) patients demonstrated both T-cell clonotypes. These results strongly suggest that the T-cell clonotypes with Vbeta7 are major TCR Vbeta genes expressed by SART-1(690-698)-specific CTLs. Furthermore, autologous tumor cells from one of the HLA-A24(+) patients stimulated the PBMCs and regional lymph node cells (LNCs) to expand the same T-cell clonotypes as those in the SART-1(690-698)-specific CTLs. These results strongly suggest that the SART-1(690-698)-specific CTLs clearly accumulate in vivo, especially in the TILs, as a consequence of in situ antigenic stimulation by autologous tumor cells. The identification of the unique TCR Vbeta genes used by SART-1(259)-specific CTLs should help to improve the diagnosis of the specific immune response in patients with SART-1(259) (+) cancers, especially during anticancer immunotherapy.

Effect of linomide on gut immune cell distribution and on TNF-alpha in plasma and ascites: an experimental study in the septic rat

A significant reduction of the pan T lymphocytes as well as CD4+ and CD8 subsets of cells in the gut mucosa of the septic rats has previously been demonstrated. In contrast, the populations of major histocompatibility complex (MHC) class II-positive cells and macrophages increased. The aim of this study was to evaluate if the immunomodulator Linomide influenced the immune cell distribution in the small intestinal mucosa in sepsis and, furthermore, if these changes coincide with changes in the concentration of tumor necrosis factor-alpha (TNF-alpha) in plasma or ascites. Polymicrobial sepsis was induced in rats by cecal ligation and puncture (CLP). Three different experimental groups were used: CLP, Linomide p.o. + CLP, and Linomide i.p.+ CLP, with adequate controls. Specimens were taken from the small bowel for immunohistologic staining and grading of mucosal injury. The following monoclonal antibodies were used: W3/25, OX8, R73, OX6, and ED1. All slides were examined by one "blinded" examiner. Mucosal injury was graded from 0 to 5. The immunostained tissues were also analyzed by an automatic color-based image system. All controls had a normal appearance of the mucosa (grade 0-1), whereas the septic animals had a median grade of III (II-IV) mucosal injury. Linomide i.p. + CLP decreased mucosal damage to median I (0-IV, P < 0.05). Linomide had no effects on the immune cell distribution in controls. In CLP rats, a significant reduction in both CD4+ and CD8+ T lymphocytes as well as an increased number of macrophages and MHC class II-positive cells was seen in the villi as compared with sham-operated controls (P < 0.05). Linomide attenuated these changes for CD8+ and T lymphocytes and macrophages. Sepsis caused increased concentrations of TNF-alpha in portal blood and ascites 3 h from CLP induction. This increase was attenuated by Linomide.

Cathepsin L regulates CD4+ T cell selection independently of its effect on invariant chain: a role in the generation of positively selecting peptide ligands

CD4+ T cells are positively selected in the thymus on peptides presented in the context of major histocompatibility complex class II molecules expressed on cortical thymic epithelial cells. Molecules regulating this peptide presentation play a role in determining the outcome of positive selection. Cathepsin L mediates invariant chain processing in cortical thymic epithelial cells, and animals of the I-A(b) haplotype deficient in this enzyme exhibit impaired CD4+ T cell selection. To determine whether the selection defect is due solely to the block in invariant chain cleavage we analyzed cathepsin L-deficient mice expressing the I-A(q) haplotype which has little dependence upon invariant chain processing for peptide presentation. Our data indicate the cathepsin L defect in CD4+ T cell selection is haplotype independent, and thus imply it is independent of invariant chain degradation. This was confirmed by analysis of I-A(b) mice deficient in both cathepsin L and invariant chain. We show that the defect in positive selection in the cathepsin L-/- thymus is specific for CD4+ T cells that can be selected in a wild-type and provide evidence that the repertoire of T cells selected differs from that in wild-type mice, suggesting cortical thymic epithelial cells in cathepsin L knockout mice express an altered peptide repertoire. Thus, we propose a novel role for cathepsin L in regulating positive selection by generating the major histocompatibility complex class II bound peptide ligands presented by cortical thymic epithelial cells.

The transmembrane adaptor protein TRIM regulates T cell receptor (TCR) expression and TCR-mediated signaling via an association with the TCR zeta chain

T cell receptor (TCR)-interacting molecule (TRIM) is a recently identified transmembrane adaptor protein, which is exclusively expressed in T cells. Here we demonstrate that in mature T cells, TRIM preferentially interacts with the TCR via the TCR-zeta chains and to a lesser extent via the CD3-straightepsilon/gamma heterodimer. Transient or stable overexpression of TRIM in Jurkat T cells results in enhancement of TCR expression on the cell surface and elevated induction of Ca(2+) mobilization after T cell activation. TRIM-mediated upregulation of TCR expression results from inhibition of spontaneous TCR internalization and stabilization of TCR complexes on the cell surface. Collectively, our data identify TRIM as a novel integral component of the TCR complex and suggest that one function of TRIM might be to modulate the strength of signals transduced through the TCR through regulation of TCR expression on the cell surface.

Mucosal immune network in the gut for the control of infectious diseases

The common mucosal immune system (CMIS) consists of an integrated cross-communication pathway of lymphoid tissues made up of inductive and effector sites for host protection against pathogenic microorganisms. Major effector molecules of the CMIS include IgA antibodies and cytokines, chemokines and their corresponding receptors. Secretory IgA (S-IgA), the major immunoglobulin, is induced by gut-associated lymphoreticular tissue (GALT)-derived B cells with the help of Th1- and Th2-type CD4(+) T lymphocytes. Cytotoxic T lymphocytes (CTLs) in the mucosal epithelium, a subpopulation of intraepithelial lymphocytes (IELs), also help maintain the mucosal barrier. The CMIS is unique in that it can provide both positive and negative signals for the induction and regulation of immune responses in both the mucosal and systemic compartments after oral or nasal antigen exposure. Prevention of infection through mucosal surfaces can be achieved by the CMIS through connections between inductive (e.g. GALT) and effector tissues. When vaccine antigens are enterically administered together with mucosal adjuvants [e.g. cholera toxin (CT), heat-labile toxin produced by Escherichia coli (LT) and IL-12], antigen-specific Th1/Th2 and IgA B cell responses are induced simultaneously in the mucosal effector compartment. Since these antigen-specific immune responses are not generated by oral vaccine without mucosal adjuvant, safe and effective adjuvants for the induction of antigen-specific S-IgA and CTL responses are essential for the development of mucosal vaccines for protection against infectious diseases. Finally, recent findings suggest the presence of a CMIS-independent IgA induction pathway, which also must be considered in the development of mucosal vaccines.

The involvement of the proto-oncogene p120 c-Cbl and ZAP-70 in CD2-mediated T cell activation

The CD2 co-receptor expressed on the surface of T lymphocytes is able to stimulate T cell activation, proliferation and cytokine production in the absence of direct engagement of the antigen-specific TCR. Engagement of human CD2 by mitogenic pairs of anti-CD2 mAb induces tyrosine phosphorylation of a number of intracellular proteins including a 120 kDa phosphoprotein that we identify as the proto-oncogene c-Cbl. Rapidly tyrosine phosphorylated following stimulation of a number of cell surface receptors, c-Cbl is an adaptor protein that has been shown to associate with a complex of intracellular signaling molecules, and to mediate both positive and negative regulatory effects. Here we show that, like TCR-CD3 stimulation, stimulation of CD2 enhanced the association of c-Cbl with both Crk(L) and the p85 subunit of phosphatidylinositol-3 kinase. Overexpression of wild-type c-Cbl protein inhibited both CD2and CD3-induced NF-AT transcriptional activity, suggesting that CD2 signaling is also negatively regulated by c-Cbl. The inhibitory effect of c-Cbl depended upon its N-terminal phosphotyrosine-binding domain, the domain that has been shown to be required for inhibition of the Syk/ZAP-70 family kinases. In Syk(-) Jurkat T cells stably expressing wild-type ZAP-70, CD2 stimulation induced only a minimal increase in ZAP-70 tyrosine phosphorylation. Nevertheless, ZAP-70 kinase was required for CD2-mediated NF-AT transcriptional activity. Thus, CD2-mediated NF-AT transcriptional activity appears to depend upon ZAP-70/Syk kinases and to be negatively regulated by c-Cbl.

Infection with an H2 recombinant herpes simplex virus vector results in expression of MHC class I antigens on the surfaces of human neuroblastoma cells in vitro and mouse sensory neurons in vivo

The majority of neurons in herpes simplex virus (HSV)-infected murine sensory ganglia are transiently induced to express MHC-I antigens at the cell surface, whereas only a minority are themselves productively infected. The aim of the current work was to determine whether MHC-I antigens can be expressed on the surfaces of infected neurons in addition to their uninfected neighbours. To address this aim a recombinant HSV type 1 strain, S-130, was used to deliver a mouse H2K(d) gene, under control of the HCMV IE-1 promoter/enhancer, into human neuroblastoma cells in vitro and mouse primary sensory neurons in vivo. S-130 expressed H2K(d) antigens on the surfaces of IMR-32 cells, a human neuroblastoma cell line that expresses very low levels of MHC-I constitutively. In K562 cells, which do not express MHC-I constitutively, H2K(d) and beta(2)-microglobulin (beta(2)m) were shown to be co-expressed at the cell surface following S-130 infection. This observation was taken as evidence that class I heavy chain (alphaC) molecules encoded by the expression cassette in the HSV genome were transported to the cell surface as stable complexes with beta(2)m. Significantly, after introduction of S-130 into flank skin, H2K(d) antigens were detected on the surfaces of primary sensory neurons in ganglia innervating the inoculation site. Our data show that HSV-infected murine primary sensory neurons and human neuroblastoma cells are capable of expressing cell-surface MHC-I molecules encoded by a transgene. From this, we infer that up-regulation of alphaC expression is, in principle, sufficient to overcome potential impediments to neuronal cell surface expression of MHC-I complexes.

Development of dendritic-cell based prostate cancer vaccine

Available treatments for metastatic prostate cancer have failed to demonstrate significant curative potential. Current efforts are now directed towards developments of novel strategies for the treatment of metastatic prostate cancer. Cancer immunotherapeutic strategies utilize patient immune system components to kill cancer cells. This review discusses progress in active specific immunotherapeutic approaches as potential alternative methods in the treatment of metastatic prostate cancer. One of the newest advances in cancer immunotherapy is the use of dendritic cells as the vehicle to deliver cancer antigens for an effective in vivo T cell activation. The development of dendritic cell-based prostate cancer vaccine, as well as results of several clinical trials in prostate cancer involving the administration of peptide-pulsed autologous dendritic cell pulsed are discussed.

Characterization of a newly discovered T-cell receptor beta-chain heterodimer expressed on a CD8+ bone marrow subpopulation that promotes allogeneic stem cell engraftment

The facilitating cell is a rare CD8+ bone marrow subpopulation that can enhance allogeneic hematopoietic stem cell engraftment across complete major histocompatibility complex barriers without inducing acute graft-versus-host disease. Here we describe a CD3epsilon-associated complex on the facilitating cell surface that consists of the T-cell receptor beta-chain disulfide-linked to a previously unknown 33-kilodalton glycoprotein. Provisionally called FCp33, this glycoprotein does not represent any of the known protein chains or surrogates associated with CD3-T-cell receptor beta. Expression of this CD3-T-cell receptor beta-FCp33 complex directly correlates with the facilitating cell's functional ability to enhance allogeneic stem cell engraftment in vivo.

A common T/C polymorphism in the promoter region of the beta T-cell receptor gene

Polymorphisms in the T-cell receptor genes can provide important information for the study of the immune response system, particularly for autoimmune diseases. This report characterizes a common T to C polymorphism in the promoter of the beta 2 constant chain of the T-cell receptor, which abolishes a recognition site for BglII restriction endonuclease.

Self-antigen presentation by thymic stromal cells: a subtle division of labor

Self-antigen-MHC complexes expressed by thymic stromal cells serve as ligands for TCR-mediated positive and negative selection, resulting in a self-MHC-restricted, self-tolerant T cell repertoire. It has recently become apparent that thymic stromal cells differ in their accessibility to antigen as well as their ability to process and present antigen. These differences result in the sampling by thymic stromal cells of largely nonoverlapping self-antigen pools and the display of self-peptide profiles specific for each cell type. In conjunction with single or serial cell-cell interactions between thymocytes and stromal cells, such differences in self-antigen display allow for maximal (re)presentation of 'self' in the thymus and optimize the efficacy of positive and negative selection.

Increased absolute number but not proportion of gamma/delta T-lymphocytes in the bronchoalveolar lavage fluid of patients with active pulmonary tuberculosis

SETTING

The proportions and absolute cell count of gamma/delta T-lymphocytes in the peripheral blood of patients with pulmonary tuberculosis (PTB) remains controversial. Since PTB is an infections airway disease, bronchoalveolar T-lymphocytes should be a better indicator of local immune T-cell reaction after TB infection than peripheral blood T-lymphocytes.

OBJECTIVE

To quantitate the absolute cell count and proportions of gamma/delta T-lymphocytes in the bronchoalveolar lavage fluid (BALF) of patients with active PTB.

DESIGN

Bronchoalveolar lavage (BAL) and analysis of lymphocytes in the BALF was performed in 25 patients with active PTB and 16 normal controls. All of the patients were negative for HIV infection and none was immunocompromised. BALF and blood were prepared for cell differential count and flow cytometry analysis using monoclonal antibodies CD3, CD4, CD8, CD25, HLA-DR and gamma/delta as well as alpha/beta T-lymphocyte receptors.

RESULTS

The number of cells per volume of recovered BALF was significantly higher in the patients with active PTB than in normal controls. BALF from active PTB patients also showed increased percentage of lymphocytes and neutrophils. The absolute number of total lymphocytes, CD3+ lymphocytes and CD3+ gamma/delta T-lymphocytes were significantly higher in the BALF, but not in the blood, of patients with TB, however, the proportions of CD3+ gamma/delta T-lymphocytes in BALF of patients with TB was comparable to that of normal controls. gamma/delta T-lymphocytes in the BALF rarely expressed CD4, CD25, and HLA-DR in both groups.

CONCLUSION

These results suggest that gamma/delta T-lymphocytes are not the major subpopulation of CD3+ lymphocytes in the BALF that react to mycobacterial infection in the patients with clinically established active TB.

Establishment of fully xenogeneic (mouse-->rat) bone marrow chimeras: evidence for normal development and clonal deletion of mouse T cells

BACKGROUND

Xenotransplantation is a potential solution to the critical shortage of transplantable organs. However, conventional immunosuppressive agents do not control the vigorous cellular and humoral rejection across species disparities. The induction of donor specific tolerance via bone marrow chimerism may be a method to avoid xenograft rejection. In xenogeneic chimeras, T cell repertoire selection plays an important role in the induction of tolerance. Until now a model of mouse-->rat multilineage chimerism has not been reported. This study reports the establishment of fully xenogeneic mouse-->rat multilineage chimeras and evaluates the role of T cell development and repertoire selection in tolerance induction in a xenogeneic environment.

METHODS

Recipient rats were irradiated at a dose of total body irradiation ranging between 800-1100 cGy and injected with 120-300x10(6) donor mouse bone marrow cells. Chimeras were typed for engraftment at 4 weeks and then monthly thereafter. T cell repertoire was evaluated in chimeras using two-color flow cytometry and monoclonal antibodies directed against the variable portion of the beta chain of the T cell receptor.

RESULTS

Fully xenogeneic multilineage bone marrow chimerism was produced in a mouse-->rat model by using ablative radiation and a high dose of donor cells. Mouse T cells develop in a phenotypically normal fashion in chimeric rats and the host rat is capable of deleting T cells that are reactive to the donor mouse strain.

CONCLUSION

Long-term multilineage bone marrow chimerism can be produced in a mouse-->rat bone marrow transplant model. Mouse T cells develop in a phenotypically normal fashion and negative selection of specific T cell receptor-Vbeta occurs in a xenogeneic environment in a predictable fashion paralleling that for syngeneic or allogeneic transplantation.

Major histocompatibility complex class I peptide-pulsed host dendritic cells induce antigen-specific acquired thymic tolerance to islet cells

BACKGROUND

As T-cell receptor-major histocompatibility complex (MHC) class I/self peptide interaction regulates T-cell development in the thymus, we reasoned that presentation of peptides by self dendritic cells (DC) to developing T cells in the thymus might induce acquired thymic tolerance. This hypothesis is based on the finding that intrathymic injection of allopeptides in the adult animal induces acquired tolerance. To examine this hypothesis, we studied the effects of intrathymic (IT) injection of a single immunodominant Wistar-Furth (WF) MHC class I (RT1.Au) peptide-pulsed host DC on islet allograft survival in the WF-to-ACI rat combination.

METHODS

Bone marrow-derived ACI DC expressing MHC class I and II, OX62, and ED2 present allopeptides to naive and specifically peptide-primed syngeneic T cells in mixed lymphocyte reaction. Host DC pulsed with RT1.Au peptide 5 (residues 93-109) were injected into the thymus of streptozotocin-induced diabetic ACI that were transplanted 7 days later with donor-type (WF) or third-party (Brown Norway [BN]) islets.

RESULTS

Whereas IT injection of 300 microg of peptide 5 alone led to normoglycemia and permanent islet survival in three of six diabetic ACI recipients, similar treatment combined with simultaneous intraperitoneal injection of 0.5 ml of anti-lymphocyte serum (ALS) on day -7 led to 100% permanent islet allograft survival (>200 days) compared to a mean survival time of 15.0+/-2.3 days in controls treated with ALS alone. In contrast, similarly prepared animals rejected the third-party (BN) islets in an acute fashion. To address the question of indirect allorecognition in acquired thymic tolerance, we examined the effect of peptide-pulsed host DC on graft survival. Whereas IT injection of peptide-pulsed host DC alone resulted in permanent islet survival in two of five animals, IT injection of peptide-pulsed host DC combined with 0.5 ml of ALS induced 100% donor-specific permanent islet allograft survival in the WF-to-ACI rat combination. These results suggest that thymic DC take up, process, and present the administered peptide to the developing T cells by the indirect allorecognition pathway in the induction of acquired thymic tolerance.

CONCLUSION

We have demonstrated a novel approach to inducing transplant tolerance to islet allografts with IT injection of allopeptide-pulsed host DC. This finding suggests that immunization strategies using DC expressing MHC allopeptides or peptide analogue might be potentially useful in the treatment of autoimmune diabetes mellitus.

Local adenovirus-mediated CTLA4-immunoglobulin expression suppresses the immune responses to adenovirus vectors in the brain

The effect of local administration of two adenovirus vectors, one of which expressed CTLA4-immunoglobulin (AdCTLA), which blocks the B7-CD28 co-stimulatory pathway of T cell activation in the inflammatory response to adenovirus vectors was investigated. Mice injected with AdCTLA and an E1-deleted adenovirus vector that encodes the lacZ gene (AdRL) into the brain showed inflammatory cell infiltration from the early phase until day 6 after injection that was not different from that seen in control mice injected with an E1-deleted adenovirus vector containing no transgene (Ad0) and AdRL. After day 6 the inflammation in the control mice increased, peaked by day 15 and then decreased gradually but persisted until day 60. By contrast, in mice treated with AdCTLA and AdRL the inflammation, especially T cell infiltration, was suppressed after day 15. The anti-adenovirus antibody titer increased gradually until day 60 in the Ad0-AdRL control group, and whereas the mice injected with AdCTLA and AdRL showed lower anti-adenovirus antibody titers than the control group mice after day 15. Neutralizing antibody was not detected in either group. Expression of beta-galactosidase, the gene product of AdRL, at the injection site in the striatum and corpus callosum peaked on day 6 and remained until day 60 although it was very low in both groups; beta-galactosidase expression was similar in the two groups in spite of the difference in the degree and extent of the local immune response in the brain. This study demonstrated that the injection of an adenovirus vector expressing CTLA4-immunoglobulin into the brain suppressed not only local cell infiltration in the brain but also reduced the humoral immune response to adenovirus vectors.

Progress in active specific immunotherapy of prostate cancer

Treatments available for metastatic prostate cancer have failed to demonstrate significant curative potential. Current efforts are now directed towards developments of novel strategies for the treatment of metastatic prostate cancer. Cancer immunotherapeutic strategies utilize patient immune system components to kill cancer cells. This review discusses progress in active specific immunotherapeutic approaches as potential alternative methods in the treatment of metastatic prostate cancer. Various methods of augmenting the immune response against prostate cancer are discussed including systemic cytokine adjuvant therapy, cytokine gene transduced tumor vaccines, non-antigen specific immunization, DNA and peptide vaccines plus adjuvants, as well as dendritic cell-based cancer vaccines.

Expression of costimulatory molecules CD80 and CD86 and their receptors CD28, CTLA-4 on malignant ascites CD3+ tumour-infiltrating lymphocytes (TIL) from patients with ovarian and other types of peritoneal carcinomatosis

Costimulation of T lymphocytes by the leucocyte surface molecules CD80 and CD86 expressed on antigen-presenting cells (APC) is required for the development of T cell responses. The CD28 and CTLA-4 molecules on T cells serve as receptors for the CD80 and CD86 costimulatory antigens. We have examined the frequency of expression of CD80 (B7.1), CD86 (B7.2), CD28 and CTLA-4 surface antigens on TIL isolated from malignant ascites or peritoneal washings of 26 patients with ovarian carcinoma and five patients with non-ovarian peritoneal carcinomatosis. Expression of CD80 and CD86 antigen was detected by reverse transcription-polymerase chain reaction (RT-PCR), and by FACS analysis. Significantly higher proportions of intraperitoneal CD3+ cells expressed CD86 antigen than the CD80 antigen (14 +/- 9% versus 3 +/- 3%, P < 0.05). Moreover, CD3+CD86+ cells were significantly more frequent in the peritoneal fluid (14 +/- 9%) than in the peripheral blood (3 +/- 0.4%, P < 0.05) of ovarian patients or normal controls (3 +/- 1%). CTLA-4 and CD28 antigen were expressed, respectively, on 9 +/- 4% and 86 +/- 14% of ascitic CD3+ cells of ovarian cancer patients. Both CD80 and CD86 antigens were expressed primarily on HLA-DR+ ascites TIL and were present in a very low proportion of HLA-DR- ascites TIL. These HLA-DR+ cells may represent a population of lymphocytes that have been activated in vivo, and function as APC. An anti-CD86 MoAb or a combination of anti-CD86 and anti-CD80 MoAbs significantly inhibited the proliferation of cultured intraperitoneal TIL. We have shown that in addition to CD28 and CTLA-4, CD3+ intraperitoneal TIL express the costimulatory molecules CD80 and CD86. The expression of these molecules on T cells could be dependent upon certain factors in the tumour microenvironment that could determine the outcome of in vivo immune responses.

Non-productive human TCR beta chain genes represent V-D-J diversity before selection upon function: insight into biased usage of TCRBD and TCRBJ genes and diversity of CDR3 region length

The aim of the study was to assess the influence of constraints of V-D-J rearrangement on the nonrandom junctional diversity of productive T-cell receptor beta-chain genes in peripheral T-cells. Mature peripheral T lymphocytes are expected to display a biased repertoire of T cell receptors (TCRs), enriched for those that can recognize peptides presented by the major histocompatibility complex (MHC) molecules. Therefore, functional TCR rearrangements of peripheral T-cells are unsuitable to reveal the bias of the TCR repertoire, introduced by V-D-J rearrangement. To overcome this problem, we have studied nonfunctional TCR genes representing a repertoire of rearranged TCR gene sequences without any known post-rearrangement selection. Detailed molecular analysis of a database generated from more than 500 functional (TCRBV20S1) and nonfunctional (TCRBV10S1P and TCRBV19S1P) T-cell receptor genes from peripheral blood T-cells permitted a comparative analysis of recombination frequencies of each germline-encoded V, D, and J-segments, as well as exonucleolytic nibbling and addition of nucleotides in functional and nonfunctional transcripts. Our data demonstrate that V-D-J recombination generates a more diverse CDR3 length distribution than found among productive TCRBV genes, suggesting that selection constrains the CDR3 to an optimal junctional region length. Furthermore, the well established biased patterns of D- and J-usage in the rearranged TCRBV genes in human peripheral blood lymphocytes were also present in nonfuncrional transcripts. Therefore, V-D-J diversity is biased mainly by constraints of the rearrangement process rather than intrathymic T-cell selection and peripheral expansion of particular T-cell clones.

Class I MHC molecules on hematopoietic cells can support intrathymic positive selection of T cell receptor transgenic T cells

The identity of cells that mediate positive selection of CD8(+) T cells was investigated in two T cell receptor (TCR) transgenic systems. Irradiated beta(2)-microglobulin mutant mice or mice with mutations in both the K(b) and D(b) genes were repopulated with fetal liver cells from class I(+) TCR transgenic mice. In the case of the 2C TCR, mature transgene-expressing CD8(+) T cells appeared in the thymuses of the chimeras and in larger numbers in the peripheral lymphoid organs. These CD8(+) T cells were functional, exhibited a naive, resting phenotype, and were mostly thymus-dependent. Their development depended on donor cell class I expression. These results establish that thymic hematopoietic cells can direct positive selection of CD8(+) T cells expressing a conventional TCR. In contrast, no significant development of HY (male antigen)-TCR(+) CD8(+) T cells was observed in class I(+) into class I-deficient chimeras. These data suggest that successful positive selection directed by hematopoietic cells depends on specific properties of the TCR or its thymic ligands. The possibility that hematopoietic cell-induced, positive selection occurs only with TCRs that exhibit relatively high avidity interactions with selecting ligands in the thymus is discussed.

Differential effects of transferrin receptor blockade on the cellular mechanisms involved in graft rejection

Since transferrin receptor (TfR) appears on activated T cells following the interaction of the antigen-major histocompatibility complex (MHC) with the T cell receptor (TCR) and the appearance of interleukin (IL)-2R, we therefore hypothesize that in vivo blockade of TfR prolongs allograft survival by altering the cellular mechanisms involved in graft rejection. Previous results in our laboratory have demonstrated that anti-TfR monoclonal antibody (mAb) at 100 microg on days 0 and 1 of transplantation significantly prolonged allograft survival to 25.7 +/- 0.9 days in a murine heterotopic, nonvascularized cardiac allograft model. In the current studies, administration of anti-TfR mAb at the time of maximal TfR expression, on days 2 and 3 post-transplantation, failed to prolong allograft survival (13.0 +/- 0.0 days) compared to the isotype controls (10.5 +/- 0.5 and 10.7 +/- 0.4 days) (p < 0.01, Wilcoxon rank sum). A 4-day course of anti-TfR mAb significantly prolonged allograft survival compared to the isotype controls, but was no more effective than a 2-day course of the mAb. Anti-TfR mAb suppressed the mixed lymphocyte response to donor-specific and third-party alloantigen by 78.7% (p < 0.05) and 80.8% (p < 0.05), respectively, while stimulating the CTL response to donor-specific (16.3%, p < 0.05) and third party (49.3%, p < 0.01) alloantigen. Anti-TfR mAb suppressed IL-15 and increased IL-4 intragraft mRNA expression when compared to the isotype controls. Examination of cell surface receptors important during T cell activation revealed alterations in expression following anti-TfR mAb treatment. Anti-TfR mAb is an effective immunosuppressant prolonging allograft survival by altering cell-mediated immune responses and the intragraft cytokine micro-environment.

Cell surface expression of H2 antigens on primary sensory neurons in response to acute but not latent herpes simplex virus infection in vivo

CD8(+) T lymphocytes and class I major histocompatibility complex (MHC-I) molecules profoundly influence the severity of neuronal herpes simplex virus (HSV) infection in experimentally infected mice. Paradoxically, neurons are classically regarded as MHC-I deficient. However, it is shown here that H2-encoded heavy chains (alphaCs) and their associated light chain, beta2 microglobulin, are present on the surfaces of primary sensory neurons recovered from sensory ganglia within 1 to 2 weeks of HSV infection. During this time, some neurons are found to be tightly associated with T cells in vivo. Prior data showed that termination of productive HSV infection in the peripheral nervous system is not dependent on cell-mediated lysis of infected neurons. Consistent with these data, immunogold electron microscopy showed that the density of cell surface H2 on neurons is an order of magnitude lower than on satellite glia, which is predicted to favor a noncytolytic CD8 cell response.

Vaccine therapy for prostate cancer

Vaccine therapy may provide an alternative for prostate cancer patients whose disease no longer responds to hormone therapy. Administration of dendritic cells pulsed with prostate-specific membrane antigen (PSMA) induces cellular immune responses against the tumor with virtually no adverse effects. About 30% of the evaluable patients were identified as partial responders, based on the National Prostate Cancer Project (NPCP) criteria. In addition, there was a 50% decrease of serum prostate-specific antigen or resolution of previously measurable lesions on imaging. Dendritic cell vaccine therapy may have a synergistic effect, when combined with other therapies.

Cross-Recognition of Two Middle T Protein Epitopes by Immunodominant Polyoma Virus-Specific CTL

We recently identified the immunodominant epitope for polyoma virus-specific CTL as the Dk-associated peptide MT389–397 derived from the middle T (MT) viral oncoprotein. Another Dk-restricted peptide corresponding to residues 236–244 of MT was recognized by nearly all MT389–397-reactive CTL clones, but required concentrations at least 2 logs higher to sensitize syngeneic target cells for lysis. Except for identity at the three putative Dk-peptide anchor residues, MT236–244 shares no homology with MT389–397. Using a novel europium-based class I MHC-peptide binding immunoassay, we determined that MT236–244 bound Dk 2–3 logs less well than MT389–397. Infection with a mutant polyoma virus whose MT is truncated just before the MT389–397 epitope or immunization with MT389–397 or MT236–244 peptides elicited CTL that recognized both MT389–397 and MT236–244. Importantly, infection with a polyoma virus lacking MT389–397 and mutated in an MT236–244 Dk anchor position induced polyoma virus-specific CTL recognizing neither MT389–397 nor MT236–244 epitopes. Despite predominant usage of the Vβ6 gene segment, MT389–397/MT236–244 cross-reactive CTL clones possess diverse complementarity-determining region 3β domains; this is functionally reflected in their heterogeneous recognition patterns of alanine-monosubstituted MT389–397 peptides. Using Dk/MT389–397 tetramers, we directly visualized MT236–244 peptide-induced TCR down-modulation of virtually all MT389–397-specific CD8+ T cells freshly explanted from polyoma-infected mice, suggesting that a single TCR recognizes both Dk-restricted epitopes. The availability of immunodominant epitope-specific CTL capable of recognizing a second epitope in MT, a viral protein essential for tumorigenesis, may serve to amplify the CTL response to the immunodominant epitope and prevent the emergence of immunodominant epitope-loss viruses and virus-induced tumors.

Peripheral blood T-cell receptor beta-chain V-repertoire in atopic dermatitis patients after in vitro exposure to Pityrosporum orbiculare extract

The yeast Pityrosporum orbiculare belongs to the normal cutaneous flora but is also considered to be one of the factors that may contribute to atopic dermatitis (AD). In the present study we investigated the possibility that P. orbiculare can act with superantigen activity in AD. P. orbiculare-reactive T-cell lines (TCLs) were obtained after stimulation of peripheral blood mononuclear cells (PBMC) with P. orbiculare extract. T-cell receptor beta-chain V-segment (TCRBV) usage was investigated using monoclonal antibodies and flow cytometry. We could not find any difference in TCRBV usage between AD patients (n = 10) and healthy controls (n = 5), either in fresh PBMC or in P. orbiculare-reactive TCLs. Compared with their original PBMCs the P. orbiculare-reactive TCLs showed a decreased usage of several TCRBVs, although increased usage of certain TCRBVs could be seen in some of the individuals. Further analysis of the CDR3-length polymorphism exhibited a shift in CDR3-length distribution, indicating oligoclonal expansion of T cells specific to different antigens in the P. orbiculare extract. In conclusion we have not found any evidence for superantigen activity in P. orbiculare extract, but our data support the importance of classical major histocompatibility complex (MHC)-restricted allergens in P. orbiculare.

The memory cytotoxic T-lymphocyte (CTL) response to human cytomegalovirus infection contains individual peptide-specific CTL clones that have undergone extensive expansion in vivo

Human cytomegalovirus (HCMV)-specific CD8(+) cytotoxic T lymphocytes (CTL) appear to play an important role in the control of virus replication and in protection against HCMV-related disease. We have previously reported high frequencies of memory CTL precursors (CTLp) specific to the HCMV tegument protein pp65 in the peripheral blood of healthy virus carriers. In some individuals, the CTL response to this protein is focused on only a single epitope, whereas in other virus carriers CTL recognized multiple epitopes which we identified by using synthetic peptides. We have analyzed the clonal composition of the memory CTL response to four of these pp65 epitopes by sequencing the T-cell receptors (TCR) of multiple independently derived epitope-specific CTL clones, which were derived by formal single-cell cloning or from clonal CTL microcultures. In all cases, we have observed a high degree of clonal focusing: the majority of CTL clones specific to a defined pp65 peptide from any one virus carrier use only one or two different TCRs at the level of the nucleotide sequence. Among virus carriers who have the same major histocompatibility complex (MHC) class I allele, we observed that CTL from different donors that recognize the same peptide-MHC complex often used the same Vbeta segment, although other TCR gene segments and CDR3 length were not in general conserved. We have also examined the clonal composition of CTL specific to pp65 peptides in asymptomatic human immunodeficiency virus-infected individuals. We have observed a similarly focused peptide-specific CTL response. Thus, the large population of circulating HCMV peptide-specific memory CTLp in virus carriers in fact contains individual CTL clones that have undergone extensive clonal expansion in vivo.

Cutting Edge: Immunoregulation of Th Cells by Naturally Processed Peptide Antagonists

Th cells recognize protein Ags as short peptides bound to MHC class II molecules. Altered peptide ligands can antagonize (inhibit) T cell responses to stimulatory peptides. Peptides generated by APC may contain peptide flanking residues (PFR), which lie outside the minimal binding epitope and can be recognized by the TCR. Our data show that PFR-dependent T cells were found to be potently antagonized by peptides that lack PFR and responded poorly to native protein or the immunogenic epitope delivered by a recombinant influenza virus. These data provide the first evidence that Ag processing generates both stimulatory and antagonist peptides from a single immunogenic epitope, an observation that may have important implications for T cell immunoregulation and autoimmunity.

Selective Accumulation of Related CD4+ T Cell Clones in the Synovial Fluid of Patients with Rheumatoid Arthritis

The role of T cells in the pathogenesis of rheumatoid arthritis (RA), especially in the perpetuation of advanced disease, remains unclear. Previous studies have focused on the TCR repertoire of synovial T cells in an attempt to determine whether the pattern of expression is characteristic of Ag-stimulated populations. However, the results of past studies have been conflicting. In the present work, we have undertaken an extensive analysis of the TCRs expressed by CD4+ T cells freshly isolated from synovial fluid of different joints and blood in three patients with established RA. Despite marked heterogeneity of synovial TCR expression, the results showed that 20 to 30% of the TCR β-chain gene (TCRB) sequences found in one joint were also expressed in a second joint, but not in peripheral blood T cells of the same individual. Analysis of expressed TCRB complementarity-determining region 3 sequences showed the presence of multiple expanded clonal populations that were not predicted by quantitation of β-chain variable region (Vβ) expression by immunofluorescence staining. These studies also demonstrated sets of related, but different, complementarity-determining region 3 nucleotide sequences that encoded identical or highly homologous β-chain amino acid sequences. Analysis of matching T cell clones derived from the joint by limiting dilution culture confirmed coexpression of highly homologous TCR α-chain gene (TCRA) and TCRB sequences. Together, these studies suggest that a significant proportion of synovial CD4+ T cells has been selected and expanded by conventional Ag(s) in this disease.

Vbeta4(+) T cells promote clearance of infection in murine pulmonary histoplasmosis

T cells are essential for controlling infection with Histoplasma capsulatum. Because the T cell receptor is vital for transducing the biological activities of these cells, we sought to determine if exposure to this fungus induced an alteration in the Vbeta repertoire in lungs of C57BL/6 mice infected intranasally. Vbeta2(+) cells were elevated on day 3 after infection; Vbeta4(+) cells were higher than controls on days 7, 10, and 14 after infection. Vbeta10(+) cells were increased on days 14 and 21, and Vbeta11(+) exceeded controls only on day 14. We investigated the clonality and function of Vbeta4(+) cells because their expansion transpired during the critical time of infection, that is, when cellular immunity is activated. Sequence analysis demonstrated preferential use of a restricted set of sequences in the complementarity-determining region 3. Elimination of Vbeta4(+) cells from mice impaired their ability to resolve infection. In contrast, depletion of Vbeta7(+) cells, the abundance of which was similar to that of Vbeta4(+), did not alter elimination of the fungus. The identification of clonotypes of Vbeta4(+) cells suggests that a few antigenic determinants may drive proliferation of this subset, which is necessary for optimal clearance.

The T cell repertoire primed by antiviral vaccination is influenced by self-tolerance

Vaccination can elicit CD8(+) cytotoxic T lymphocytes (CTL) that recognize peptides presented by class I MHC molecules. Relatively little is known, however, about the genetic factors that shape the repertoire of T cell clonotypes responding to any given epitope. We report here that H-2(b) mice immunized with a plasmid DNA vaccine or vaccinia virus encoding for HIV-1SF2p55gag elicit CD8(+) CTL against the H-2Db-restricted immunodominant epitope (pgagb). This response involved three different T cell populations based on their recognition of alloantigens: one that cross-reacted with the alloantigen H-2Ld, one that cross-reacted with H-2Kd, and one that did not cross-react with either H-2(d) or H-2(k) molecules. Using the TAP-deficient cell line T2-Ld, we showed that pgagb-specific CTL cross-react with H-2Ld and a yet unidentified self-peptide. In mice expressing H-2(b) and H-2(d) allotypes, we investigated whether tolerance to H-2(d) influenced the HIVp55gag-specific CTL repertoire as a consequence of thymic deletion of the cross-reactive CTL repertoire. In (H-2(dxb))F1 mice heterogygosity at the MHC-I level prevented maturation of some but not all TCR combinations specific for H-2Db+pgagb, illustrating the concept that self-tolerance can influence the repertoire of antiviral T cells.

T-cell receptor Valpha gene expression of infiltrating T cells in pancreatic cancer

BACKGROUND

T lymphocytes play a central role in the immune response to cancer, with specific T-cell reactivity provided by the T-cell receptor (TCR) alphabeta-chain heterodimer. Whereas human pancreatic adenocarcinoma is characterized by a massive infiltration of T lymphocytes, to date no analysis of the TCR Valpha-gene expression of the tumor-infiltrating lymphocytes in pancreatic cancer has been performed.

METHODS

Using reverse transcriptase polymerase chain reaction (RT-PCR) followed by dot blot hybridization, we determined the TCR alpha-chain repertoire at the mRNA level in pancreatic carcinoma and compared our findings with the TCR Valpha repertoire in the normal pancreas and chronic pancreatitis.

RESULTS

A heterogeneous lowly restricted TCR Valpha repertoire was observed in pancreatic carcinomas, different from the TCR Valpha repertoire in chronic pancreatitis.

CONCLUSIONS

Pancreas-infiltrating T cells show a distinct TCR Valpha gene expression profile in normal pancreas, chronic pancreatitis, and pancreatic cancer.

Association of p59(fyn) with the T lymphocyte costimulatory receptor CD2. Binding of the Fyn Src homology (SH) 3 domain is regulated by the Fyn SH2 domain

Human CD2 is a 50-55-kDa cell surface receptor specifically expressed on the surface of T lymphocytes and NK cells. Stimulation of human peripheral blood T cells with mitogenic pairs of anti-CD2 monoclonal antibodies (mAbs) is sufficient to induce interleukin-2 production and T cell proliferation in the absence of an antigen-specific signal through the T cell receptor. CD2 has been shown previously to associate physically with the Src family protein-tyrosine kinases p56(lck) and p59(fyn). We now report that stimulation of T cells with mitogenic pairs of anti-CD2 mAbs enhanced the association of the Fyn polypeptide with the CD2 complex, whereas stimulation with single anti-CD2 mAb had minimal effect. Using glutathione S-transferase (GST) fusion proteins, we found that CD2 bound to the Src homology (SH) 3 domain of Fyn. Interestingly, the CD2-Fyn association was negatively regulated by the Fyn SH2 domain; CD2 bound poorly to GST fusion proteins expressing both the SH2 and SH3 domains of Fyn. However, the inhibitory effect of the Fyn SH2 domain on binding of the Fyn SH3 domain to CD2 was relieved by peptides containing a phosphorylated YEEI sequence that bound directly to the Fyn SH2 domain. In addition, we found that the ability of the Fyn SH2 domain to precipitate tyrosine-phosphorylated proteins, including the CD3zeta chain, was enhanced after T cell stimulation with mitogenic pairs of CD2 mAbs. Finally, overexpression of a mutated Fyn molecule, in which the ability of the Fyn SH2 domain to bind phosphotyrosine-containing proteins was abrogated, inhibited CD2-induced transcriptional activation of the nuclear factor of activated T cells (NFAT), suggesting a functional involvement of the Fyn SH2 domain in CD2-induced T cell signaling. We thus propose that stimulation through the CD2 receptor leads to the tyrosine phosphorylation of intracellular proteins, including CD3zeta itself, which in turn bind to the Fyn-SH2 domain, allowing the direct association of the Fyn SH3 domain with CD2 and the initiation of downstream signaling events.

T-cell alterations in cardiac allograft recipients after B7 (CD80 and CD86) blockade

BACKGROUND

T-cell activation requires engagement of the T cell receptor with the antigen-MHC and simultaneous ligation of the coreceptor CD28. CD28 binds both the CD80 (B7-1) and CD86 (B7-2) ligands on antigen-presenting cells. The functional role of these costimulatory pathways in transplantation is not completely understood. We tested the hypothesis that in vivo blockade of the CD28 pathway via the anti-CD80 and anti-CD86 monoclonal antibodies (mAbs) would prolong allograft survival.

METHODS

Neonatal C57BL/6J (H2b) hearts were transplanted to CBA/J (H2k) recipients in a heterotopic nonvascularized model, with anti-CD80 and/or anti-CD86 mAbs being administered intravenously at the time of allografting (day 0) and on the following day (day 1).

RESULTS

Anti-CD80 mAb (29.8+/-1.5 days) and anti-CD86 mAb (30.8+/-0.5 days) alone significantly prolonged allograft survival compared with the isotype control (10.7+/-0.4 days, P < 0.01, Wilcoxon rank sum). The concurrent (days 0 and 1) and sequential administration of anti-CD86 mAb on days 0 and 1 plus anti-CD80 mAb on days 2 and 3 prolonged allograft survival to >80 days. Simultaneous administration of anti-CD80 and anti-CD86 mAbs significantly suppressed donor-specific cytotoxic T lymphocyte responses to alloantigen. Anti-CD86 mAb suppressed intragraft interleukin (IL)-4, IL-10, IL-12 p40, and IL-15 mRNA expression.

CONCLUSIONS

Anti-CD80 and/or anti-CD86 mAbs are potent immunosuppressants in prolonging allograft survival. Combined blockade of the B7 (CD80 and CD86) ligands seems to be the most effective in prolonging allograft survival and suppressing donor-specific allogeneic cytotoxic T lymphocyte responses. In vivo blockade of CD86, in comparison to CD80, had the greatest immunosuppressive effect on day 7 intragraft cytokines, suggesting its role on early allogeneic immune responses.

Cathepsin L: critical role in Ii degradation and CD4 T cell selection in the thymus

Degradation of invariant chain (Ii) is a critical step in major histocompatibility complex class II-restricted antigen presentation. Cathepsin L was found to be necessary for Ii degradation in cortical thymic epithelial cells (cTECs), but not in bone marrow (BM)-derived antigen-presenting cells (APCs). Consequently, positive selection of CD4+ T cells was reduced. Because different cysteine proteinases are responsible for specific Ii degradation steps in cTECs and BM-derived APCs, the proteolytic environment in cells mediating positive and negative selection may be distinct. The identification of a protease involved in class II presentation in a tissue-specific manner suggests a potential means of manipulating CD4+ T cell responsiveness in vivo.

Antigen processing and autoimmunity. Evaluation of mRNA abundance and function of HLA-linked genes

Quantitative defects in the density of conformationally correct human lymphocyte antigen (HLA) class I complexes on the surface of lymphocytes are apparent in patients with diverse HLA-linked autoimmune diseases, including Type I diabetes and Sjögren's syndrome. First, HLA class I expression was investigated in individuals with two rare and genetically divergent polyglandular autoimmune diseases. Polyglandular failure patients whose disease showed HLA linkage, but not those whose disease was not HLA linked, exhibited decreased HLA class I expression on the surface of their lymphocytes as well as a reduced abundance of transcripts of the HLA-linked genes Tap1 and Tap2, both of which encode proteins that contribute to HLA class I processing. Second, lymphocytes from patients with insulin-dependent diabetes mellitus (IDDM), Sjögren's syndrome, Graves' disease, and Hashimoto's disease showed varying degrees of decreased abundance of mRNAs that encode Tap1, Tap2, Lmp2, or Lmp7 (the latter two proteins also contribute to HLA class I processing). Third, in twins discordant for IDDM, reduced transcript abundance was preferential to diabetic subjects. Fourth, functional assays of isolated diabetic proteasomes, the peptide cutting complex containing LMP2 and LMP7 proteins, revealed altered peptidase activity. These data suggest that defective transcription of HLA class I-processing genes could contribute to the quantitative defect in cell-surface expression in autoimmune lymphocytes of HLA-controlled disease.

Anti-transferrin receptor monoclonal antibody: a novel immunosuppressant

BACKGROUND

Transferrin receptor is a widely distributed cell surface receptor present on most proliferating and highly specialized quiescent cells. Expression of transferrin receptor on the surface of immune cells is up-regulated during T-cell activation after the interaction of the antigen-MHC with the T cell receptor. The role of transferrin receptor in T-cell activation has not been well-established. Since transferrin receptor is physically associated with the CD3 zeta-chain, blockade of transferrin receptor has the potential to interfere with the T-cell signals important in transplant rejection.

METHODS

Anti-transferrin receptor monoclonal antibody (mAb) was administered in vivo and in vitro to determine whether this agent was effective in prolonging allograft survival and altering cell-mediated immunity.

RESULTS

Using donor C57BL/6J (H2b) hearts transplanted to CBA/J (H2k) recipients, anti-transferrin receptor mAb at the time of transplantation prolonged cardiac allograft mean survival time to 25.7+/-0.9 days compared with untreated (13.3+/-0.6 days, P < 0.05) or isotype-matched (10.7+/-0.4 days, P < 0.05) controls. Anti-transferrin receptor mAb administered in vivo failed to suppress the subsequent allogeneic responses. However, when added to culture, anti-transferrin receptor mAb suppressed the allogeneic cytotoxic T lymphocyte response by 79-100% but not the mixed lymphocyte response.

CONCLUSIONS

These studies are the first to suggest that transferrin receptor is a potential therapeutic target for clinical transplantation. Future studies will determine the most efficacious dose and time for maximal immunosuppression and the mechanisms responsible for the immunosuppression exhibited by antitransferrin receptor mAb.

Limited T cell receptor Vbeta-chain repertoire of liver-infiltrating T cells in autoimmune hepatitis

BACKGROUND/AIMS

To characterize the cellular immune reactions in autoimmune hepatitis, the T cell receptor repertoire of liver-infiltrating and circulating T cells was studied.

METHODS

Nucleic acids of liver-tissue and peripheral blood-derived T cells from 12 patients with untreated autoimmune hepatitis, four patients with chronic hepatitis C and three patients with toxic liver injury were extracted and analysed using a semiquantitative RT-PCR with a panel of T cell receptor Vbeta family specific primers. After agarose gel electrophoresis, the distribution of T cell receptor (TCR) Vbeta molecules was assessed by densitometry. Furthermore, results were compared to the TCR Vbeta distribution of 10 healthy blood donors.

RESULTS

Four of 12 patients with untreated autoimmune hepatitis but no patients with chronic hepatitis C and toxic liver injury showed a significant overexpression of TCR Vbeta3 (17.8% +/- 2.6% vs. 9.3% +/- 4.6%; p = 0.01) and three an overexpression of Vbeta13.1 (14.6% +/- 2.3% vs. 6.6% +/- 3.5%; p = 0.02) molecules compared to the TCR Vbeta-distribution in healthy blood donors. In addition, Vbeta3+ T cells were found enriched in the liver tissue compared to autologous peripheral blood in three autoimmune hepatitis patients (15.3% +/- 7.0% vs. 5.2% +/- 3.1%; L/B ratio: 2.9), while Vbeta13.1+ T cells were enriched in the liver tissue from one of three patients with overexpression.

CONCLUSIONS

In autoimmune hepatitis a disease specific compartmentalisation of TCR Vbeta3+ T cells was observed in the liver tissues. Although their specificity was unknown, this might indicate that these infiltrating T cells could have relevance for abnormal immunoregulation.

Etiology of sarcoidosis

Since sarcoidosis was first recognized as a distinct clinical entity, investigators have speculated that a transmissible agent may cause sarcoidosis. Recent attempts at directly isolating infectious organisms or indirectly detecting microbial DNA or RNA from sarcoid tissue have led to inconclusive results. Studies on the immunopathogenic origins of sarcoidosis have provided evidence of persistent antigenic stimulation at sites of inflammation that are associated with dysregulated cytokine production. To date, however, the challenge of defining the cause of sarcoidosis remains unmet.

Topology of T cell receptor-peptide/class I MHC interaction defined by charge reversal complementation and functional analysis

The molecular interactions between the CD8 co-receptor dependent N15 and N26 T cell receptors (TCRs) and their common ligand, the vesicular stomatitis virus octapeptide (VSV8) bound to H-2Kb, were studied to define the docking orientation(s) of MHC class I restricted TCRs during immune recognition. Guided by the molecular surfaces of the crystallographically defined peptide/MHC and modeled TCRs, a series of mutations in exposed residues likely contacting the TCR ligand were analyzed for their ability to alter peptide-triggered IL-2 production in T cell transfectants. Critical residues which diminished antigen recognition by 1000 to 10,000-fold in molar terms were identified in both N15 Valpha (alphaE94A or alphaE94R, Y98A and K99) and Vbeta (betaR96A, betaW97A and betaD99A) CDR3 loops. Mutational analysis indicated that the Rp1 residue of VSV8 is critical for antigen recognition of N15 TCR, but R62 of H-2Kb is less critical. More importantly, the alphaE94R mutant could be fully complemented by a reciprocal charge reversal at Kb R62 (R62E). This result suggests a direct interaction between N15 TCR Valpha E94R and Kb R62E residues. As Rp1 of VSV8 is adjacent to R62 in the VSV8/Kb complex and essential for T cell activation, this orientation implies that the N15 Valpha CDR3 loop interacts with the N-terminal residues of VSV8 with the Valpha domain docking to the Kb alpha2 helix while the N15 Vbeta CDR3 loop interacts with the more C-terminal peptide residues and the Vbeta domain overlies the Kb alpha1 helix. An equivalent orientation is suggested for N26, a second VSV8/Kb specific TCR. Given that genetic analysis of two different class II MHC-restricted TCRs and two crystallographic studies of class I restricted TCRs offers a similar overall orientation of V domains relative to alpha-helices, these data raise the possibility of a common docking mode between TCRs and their ligands regardless of MHC restriction.

CD28 blockade alters cytokine mRNA profiles in cardiac transplantation

BACKGROUND

T-cell response to alloantigen is dependent on T-cell receptor activation and costimulation through the CD28 receptor, because T-cell receptor activation alone is insufficient for optimal immune response. The CD28 receptor on helper T cells interacts with its ligand B7 on activated B cells-macrophages as costimulus to support T-cell activity. CTLA4Ig is a recombinant inhibitor of CD28 receptor activation. In vivo studies with a rat major histocompatibility complex mismatch heterotopic cardiac transplant model demonstrate that CTLA4Ig prolongs cardiac allograft survival. This CTLA4Ig survival benefit is enhanced with prior donor-specific antigen exposure.

METHODS

To investigate CTLA4Ig mechanisms, we examined the differential expression of B7 and cytokine mRNAs for interferon-gamma (IFN-gamma), interleukin-2 (IL-2), IL-4, and IL-10 (Th1 or Th2 activation) in cardiac allografts after treatment with CTLA4Ig and donor-specific antigen exposure versus conventional immunotherapy (cyclosporine, cyclophosphamide, or antilymphocyte serum). In the above major histocompatibility complex mismatch model, hearts (on day 5 after transplantation at peak rejection) had cytokine mRNA expression determined by semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

Inhibition of B7 expression was observed in CTLA4Ig animals. Expression of IL-2 and IFN-gamma was near undetectable in CTLA4Ig and cyclophosphamide rats but was only moderately reduced by cyclosporine and antilymphocyte serum. IL-4 mRNA expression was reduced equally in all animals. Finally, IL-10 levels were unchanged by CTLA4Ig but were decreased by other therapies.

CONCLUSIONS

The beneficial effect of CTLA4Ig, inhibiting expression of B7, alters Th1 cytokines IL-2 and IFN-gamma, with a resultant predominant IL-10 driven, Th2 tolerogenic response.

Selective amplification of T-cell receptor variable region species is demonstrable but not essential in early lesions of psoriasis vulgaris: analysis by anchored polymerase chain reaction and hypervariable region size spectratyping

Several groups have investigated the role of T cells in the pathogenesis of psoriasis by determination of T-cell receptor (TCR) B-chain variable (V) region usage, both in chronic plaque (psoriasis vulgaris) and guttate forms, with various results. Because there are no data on TCR expression in early psoriasis vulgaris, when specific cellular immune events may be expected to be most pronounced, we have analyzed early lesions (less than 3 wk old) of ten patients, with highly reproducible results. We have developed a highly controlled anchored polymerase chain reaction (PCR) method in which TCR beta chain species are all amplified with the same primer pair and products are quantified by dot blot hybridization with BV family-specific oligonucleotide probes. Overexpression of certain TCR BV genes was observed in the majority of lesional biopsies, but in samples in which the expanded BV family formed more than 10% of total lesional BV (half of the samples analyzed), BV2 and BV6 predominated. The consistency of overexpression of these BV species between patients was much less than in previous studies of TCRBV usage in established chronic plaque psoriasis lesions. Complementarity-determining region 3 (CDR3) size spectratyping demonstrated evidence for selective clonal T cell accumulation in less than half of the lesional samples showing BV expansion. These results indicate that selective amplification of TCRBV species occurs in early psoriasis vulgaris but is not essential to the pathogenic process and may be more important in the maintenance or expansion of chronic lesions.

Differential effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin, bis(tri-n-butyltin) oxide and cyclosporine on thymus histophysiology

Recent advances in the histophysiology of the normal thymus have revealed its complex architecture, showing distinct microenvironments at the light and electron microscopic level. The epithelium comprising the major component of the thymic stroma is not only involved in the positive selection of thymocytes, but also in their negative selection. Dendritic cells, however, are more efficient than epithelial cells in mediating negative selection. Thymocytes are dependent on the epithelium for normal development. Conversely, epithelial cells need the presence of thymocytes to maintain their integrity. The thymus rapidly responds to immunotoxic injury. Both the thymocytes and the nonlymphoid compartment of the organ can be targets of exposure. Disturbance of positive and negative thymocyte selection may have a major impact on the immunological function of the thymus. Suppression of peripheral T-cell-dependent immunity as a consequence of thymus toxicity is primarily seen after perinatal exposure when the thymus is most active. Autoimmunity may be another manifestation of chemically mediated thymus toxicity. Although the regenerative capacity of thymus structure is remarkable, it remains to be clarified whether this also applies to thymus function. In-depth mechanistic studies on chemical-induced dysfunction of the thymus have been conducted with the environmental contaminants 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and bis(tri-n-butyltin)oxide (TBTO) as well as the pharmaceutical immunosuppressant cyclosporine (CsA). Each of these compounds exerts a differential effect on the morphology of the thymus, depending on the cellular targets for toxicity. TCDD and TBTO exposure results in cortical lymphodepletion, albeit by different mechanisms. An important feature of TCDD-mediated thymus toxicity is the disruption of epithelial cells in the cortex. TBTO primarily induces cortical thymocyte cell death. In contrast CsA administration results in major alterations in the medulla, the cortex remaining largely intact. Medullary epithelial cells and dendritic cells are particularly sensitive to CsA. The differential effects of these three immunotoxicants suggest unique susceptibilities of the various cell types and regions that make up the thymus.

Rapid detection of bovine type II collagen-specific T-cell hybridomas

T-cell hybridomas are powerful tools in studying the fine specificities of antigen recognition by the T-cell receptor (TCR), the structure and genetic basis of the CD3-TCR complex, and the size of the TCR alpha/beta repertoire used in response to various antigens. A technical challenge in establishing T-cell hybridomas is the early identification of antigen-specific ones. We have established a rapid and efficient ELISA method for detecting antigen-specific T-cell hybridomas. Our ELISA technique significantly reduces the time and resources required for the primary screening of antigen-specific T-cell hybrids, eliminates the need of maintaining hundreds of rapidly growing nonspecific clones, and does not require the maintenance of IL-2/IL-4 dependent cell lines such as CTLL-2 or HT-2. In addition, the ELISA technique is designed to detect both types of CD4 T-cells: Th1 and Th2, by using a mixture of anti-IL-2 and anti-IL-4 monoclonal antibodies. Therefore, we believe that our ELISA technique provides a faster, less expensive, and higher throughput screening method for the early identification of antigen-specific T-cell hybridomas than the current bioassays.

Long-term alloreactive T cell lines and clones express a limited T cell receptor repertoire

Alloreactive T cells recognize either determinants of the intact donor MHC molecules displayed on the surface of transplanted-cells or peptide fragments of donor antigens associated with self-MHC molecules by means of their T cell receptors (TCR). To investigate the relationship between the TCR beta chain structure and allorecognition, we established and characterized four long-term T cell lines and seven T cell clones derived following a mixed lymphocyte reaction (MLR) between fully histoincompatible DA (RT1a) and LEW (RT1(1)) rat lymph node cells. These DA anti-LEW T cells were phenotypically CD4+, CD8-, alpha beta TCR+ and produced interferon-gamma but not IL-4, consistent with being Th1 CD4+ T cells. As might be expected, these cells were not significantly cytotoxic and did not display suppressor activity. Analysis of the TCR beta chain gene structure revealed a very restricted repertoire in both long-term lines and clones. The TCRBV6S1 gene was present in 15/21 of the alloreactive T cell mRNA transcripts but only 1/12 of unstimulated DA splenic TCR mRNA transcripts (p = 0.0018). Similarly, the TCRBJ2S1 gene was also used frequently in the alloreactive transcripts (17/21) but in only 2/12 unstimulated splenic transcripts (p = 0.0013). Furthermore, all 15 of the alloreactive TCRBV6S1 transcripts had a distinctive four amino acid N region motif not present in any of the unstimulated TCR transcripts (p = 0.0003). These experiments reveal a distinct homogeneity amongst stable allogeneic T cells in culture. If these results reflect the situation in vivo, the possibility exists that specific immunotherapy may be successful in preventing allograft rejection.