IL-2 and TNF receptors as targets of regulatory T-T interactions: isolation and characterization of cytokine receptor-reactive T cell lines in the Lewis rat

T cells are considered to be of prime importance in immune regulation of both B and T cell functions. The targets of recognition in T-T cell interactions are not clear. Most recent experimental work has focused on the idiotypic regulatory interactions mediated by TCR peptides. There is experimental evidence that regulatory cells exist that do not recognize the TCR. This type of regulation is selectively induced by activated T cells. Therefore, we designed this study to examine the possible role of cytokine receptors as targets of immune regulation. We tested two peptides of IL-2R alpha-chain, 2 of IL-2R beta-chain, and one of TNFR (p60). All peptides were found to be immunogenic at inducing T cell proliferation and four induced Abs in Lewis rats. We generated T cell lines to these five peptides, and tested them both in vitro and in vivo. We found that the T cells exhibited a proliferative response when cultured with activated, irradiated stimulator cells that were augmented upon addition of the cytokine receptor peptide. The cytokine profile of the lines was characterized as well as the Vbeta gene composition. One of the lines significantly protected against active encephalomyelitis. These results point at cytokine receptors as possible targets of immune regulation and T-T cell interactions.

The peptide binding specificity of the MHC class II I-A molecule of the Lewis rat, RT1.BI

The specificity of peptide binding to MHC molecules is defined by binding motifs composed of several relatively conserved anchor positions. The peptide binding motifs of murine MHC class II I-A molecules are functionally important but poorly characterized. Here we use peptide binding studies and isolation of naturally presented peptides to characterize the peptide binding motif of the MHC class II I-A molecule, RT1.BI, a molecule that is involved in experimental autoimmunity in the Lewis rat. We now report that, similar to other class II motifs, the RT1.BI motif consists of a nonamer sequence with four major anchor positions (P1, P4, P6 and P9). Residues at P4 and P9, rather than at P1, appeared to be particularly important for binding. Negatively charged residues were favored at P9, consistent with the presence of a serine at position 57 of the RT1.BI beta chain. This RT1.BI motif could be observed in the dominant autoantigenic T cell epitopes mapped previously in the Lewis rat. These results highlight a general similarity and some important differences in the organization of MHC class II peptide binding motifs. The reported RT1.BI motif should facilitate the prediction and design of T cell epitopes for the induction and control of experimental autoimmune diseases in Lewis rat models.

An alpha-chain TCR CDR3 peptide can enhance EAE induced by myelin basic protein or proteolipid protein

Regulation of experimental autoimmune encephalomyelitis (EAE) can be induced by anti-idiotype immunity against T cell receptor (TCR) fragments associated with major histocompatibility complex (MHC) molecules. However, we have recently found that preimmunization with an alpha-chain TCR CDR3 peptide (LYFCAARSNYQL) derived from myelin basic protein (MBP)-specific clones did not suppress but rather augmented the severity of EAE induced by MBP-specific T cells in SJL/J mice. To test whether CDR3 vaccination could control only a highly restricted T cell population, we studied the effect of the peptide against EAE induced by T cells specific for different Ag/MHC ligands and autoimmune diseases affecting non-neural tissues. In contrast to expectations, the peptide was found to augment not only EAE induced by MBP-specific T cells, but also proteolipid protein (PLP)-specific T cell- or PLP peptide-induced EAE in SJL/J mice, and MBP-induced EAE and adjuvant arthritis (AA) in rats. The CDR3 peptide was neither inhibitory nor supportive for Ag-induced activation of an encephalitogenic clone in vitro. In addition, the peptide treatment neither inhibited the induction of Ag-specific T cells nor altered the APC function of spleen cells. These findings, on the one hand, confirm previous results showing TCR peptide-induced enhancement of the disease and, on the other hand, indicate that the TCR CDR3 peptide may control T cells with broader Ag/MHC specificities than could be expected. Structural similarity among TCR idiotypes of autoimmune T cells may partly account for these results.

The hsp60 peptide p277 arrests the autoimmune diabetes induced by the toxin streptozotocin

The development of autoimmune diabetes in the NOD strain of mice (H-2g7) is marked by the presence of T-cells reactive to the p277 peptide of the 6O-kDa heat shock protein (hsp60). We have found that the p277 peptide can be used as a therapeutic vaccine to arrest NOD diabetes. Recently, we found that T-cell autoimmunity to p277 also develops spontaneously in C57BL/KsJ mice (H-2d) during the induction of autoimmune diabetes by a very low dose of the beta-cell toxin streptozotocin (STZ). We now report the inhibition of STZ toxin-induced autoimmune diabetes by p277 peptide therapy. Administration of two doses each of 100 micrograms of peptide p277 in mineral oil given 1 week after toxin induction and 85 days later was most effective. The effect of p277 on STZ toxin-induced diabetes was marked by a shift in p277 autoimmunity from a T-cell proliferative response to the production of anti-p277 antibodies. The anti-p277 antibodies were predominantly of the IgG1 and IgG2b isotypes, known to be regulated by Th2 type cytokines; IgG2a antibody, known to be dependent on interferon (IFN)-gamma, was induced to a much lesser degree. Peptide p277 therapy was specific: treatment of the mice with an immunogenic peptide from the sequence of another antigen, GADp34, failed to prevent the development of diabetes. The GADp34 peptide induced lower titers of specific antibodies, and the antibodies were predominantly of the IgG2a class. Thus, p277 peptide therapy, marked by the induction of Th2-type antibodies, can be effective in toxin-induced autoimmune diabetes.

Suppressive vaccination with DNA encoding a variable region gene of the T-cell receptor prevents autoimmune encephalomyelitis and activates Th2 immunity

A variable region gene of the T-cell receptor, V beta 8.2, is rearranged, and its product is expressed on pathogenic T cells that induce experimental autoimmune encephalomyelitis (EAE) in H-2u mice after immunization with myelin basic protein (MBP). Vaccination of these mice with naked DNA encoding V beta 8.2 protected mice from EAE. Analysis of T cells reacting to the pathogenic portion of the MBP molecule indicated that in the vaccinated mice there was a reduction in the Th1 cytokines interleukin-2 (IL-2) and interferon-gama. In parallel, there was an elevation in the production of IL-4, a Th2 cytokine associated with suppression of disease. A novel feature of DNA immunization for autoimmune disease, reversal of the autoimmune response from Th1 to Th2, may make this approach attractive for treatment of Th1-mediated diseases like multiple sclerosis, juvenile diabetes and rheumatoid arthritis.

Lymph node cell vaccination against the lupus syndrome of MRL/lpr/lpr mice

Immunization with pathogenic lymphoid cells has been shown to induce resistance to disease in experimental animal models of cell mediated autoimmunity. In the present work we tested the effectiveness of this approach in a spontaneous murine autoimmune disease, the MRL/lpr/lpr (MRL/1) murine lupus model. We now report that the anti-DNA antibodies and glomerulonephritis of MRL/1 mice could be prevented by the adoptive transfer of spleen cells from MRL/+ mice that had been vaccinated with MRL/1 lymph node T lymphocytes, but not by direct vaccination of MRL/1 mice with their cells. These results indicate that the lupus of MRL/1 mice is susceptible to regulation by adoptive vaccination and that these autoimmune mice lack the ability to raise a suppressive response against their own pathogenic cells.

NOD mouse diabetes: the ubiquitous mouse hsp60 is a beta-cell target antigen of autoimmune T cells

In the NOD mouse, the onset of beta-cell destruction is associated with spontaneous development of T-lymphocytes reactive to members of the 60 kDa heat shock protein (hsp60) family, including the Mycobacterial (MT) and the human (H) hsp60 molecules. Diabetes in the NOD mouse is a spontaneous tissue-specific autoimmune disease occurring without prior immunization. Therefore, it has been suggested that the anti-hsp60 T cells involved in the autoimmune diabetes of NOD mice might reflect molecular mimicry between MT-hsp60 and a beta-cell tissue specific molecule sharing similar T cell epitopes, the p277 peptide of hsp60 in particular. We cloned and expressed the mouse hsp60 cDNA from a beta-cell tumour. This mouse beta-cell hsp60 cDNA was found to be identical in sequence to the hsp60 of mouse fibroblasts. We further report that NOD spleen cells and an NOD diabetogenic T cell clone C9 responded to the recombinant mouse hsp60 and to its peptide M-p277 to the same extent as to H-hsp60 and H-p277. Splenocytes of mice of other strains did not respond to p277. Moreover, treatment of 3 month old NOD mice with the non-modified self M-p277 peptide was as efficient as H-p277, from which it differs in one amino acid, in halting progression of the disease. Thus, anti-H-p277 T cells modulating diabetes in the NOD mouse are autoreactive, and are targeted at the mouse beta-cell hsp60, which is not tissue specific. These findings raise the question of how a non-tissue specific molecule may be a target of a tissue-specific autoimmune disease.

A role of Hsp60 in autoimmune diabetes: analysis in a transgenic model

A pathogenic role for self-reactive cells against the stress protein Hsp60 has been proposed as one of the events leading to autoimmune destruction of pancreatic beta cells in the diabetes of nonobese diabetic (NOD) mice. To examine this hypothesis, we generated transgenic NOD mice carrying a murine Hsp60 transgene driven by the H-2E alpha class II promoter. This would be expected to direct expression of the transgene to antigen-presenting cells including those in the thymus and so induce immunological tolerance by deletion. Detailed analysis of Hsp60 expression revealed that the endogenous gene is itself expressed strongly in thymic medullary epithelium (and weakly in cortex) yet fails to induce tolerance. Transgenic mice with retargeted Hsp60 showed overexpression of the gene in thymic cortical epithelium and in bone marrow-derived cells. Analysis of spontaneous T-cell responses to a panel of self and heterologous Hsp60 antigens showed that tolerance to the protein had not been induced, although responses to an immunodominant 437-460 epitope implicated in disease were suppressed, probably indicating an epitope shift. This correlated with changes in disease susceptibility: insulitis in transgenic mice was substantially reduced so that pathology rarely progressed beyond periislet infiltration. This was reflected in a substantial reduction in hyperglycemia and disease. These data indicate that T cells specific for some epitopes of murine Hsp60 are likely to be involved in the islet-cell destruction that occurs in NOD mice.

IL-2 rescues antigen-specific T cells from radiation or dexamethasone-induced apoptosis. Correlation with induction of Bcl-2

Most studies of apoptosis on T lymphocytes have examined the effects of various stimuli on immature T cells from the thymus. Previous work has indicated that apoptosis of mature memory T cells may be an important pathophysiologic mechanism in diseases such as AIDS, cancer, and autoimmunity. The effect of IL-2 on apoptosis of T cells is not clear. Therefore, we studied the ability of IL-2 to rescue Ag-specific T cells from apoptosis. We found that IL-2, in a dose-dependent manner, prevented T cells from entering apoptosis induced by gamma-irradiation, mitomycin C, or dexamethasone. This effect was specific for IL-2; IL-1 beta, IL-6, or IFN-gamma could not reproduce it. In contrast to Ag-specific T cells, immature T cells and naive mature peripheral T cells could not be rescued by IL-2 from radiation-induced apoptosis. Apoptosis rescue by IL-2 was associated with the induction of bcl-2 mRNA and protein. This induction could not be attributed to the effects of IL-2 on the cell cycle, as T cells that were prevented from cell cycle progression by irradiation showed a similar induction of bcl-2. Rescued cells retained their Ag-specific proliferative capacity and in vivo functions. These findings demonstrate that the apoptotic death of Ag-specific T cell lines, cells which can be regarded as a model for memory T cells, can be prevented with IL-2. This effect may have important therapeutic implications for patients receiving chemotherapy or radiotherapy, and for patients with AIDS who develop immunodeficiency primarily as a result of loss of Ag-specific memory T cells.

IL-2 rescues antigen-specific T cells from radiation or dexamethasone-induced apoptosis. Correlation with induction of Bcl-2

Most studies of apoptosis on T lymphocytes have examined the effects of various stimuli on immature T cells from the thymus. Previous work has indicated that apoptosis of mature memory T cells may be an important pathophysiologic mechanism in diseases such as AIDS, cancer, and autoimmunity. The effect of IL-2 on apoptosis of T cells is not clear. Therefore, we studied the ability of IL-2 to rescue Ag-specific T cells from apoptosis. We found that IL-2, in a dose-dependent manner, prevented T cells from entering apoptosis induced by gamma-irradiation, mitomycin C, or dexamethasone. This effect was specific for IL-2; IL-1 beta, IL-6, or IFN-gamma could not reproduce it. In contrast to Ag-specific T cells, immature T cells and naive mature peripheral T cells could not be rescued by IL-2 from radiation-induced apoptosis. Apoptosis rescue by IL-2 was associated with the induction of bcl-2 mRNA and protein. This induction could not be attributed to the effects of IL-2 on the cell cycle, as T cells that were prevented from cell cycle progression by irradiation showed a similar induction of bcl-2. Rescued cells retained their Ag-specific proliferative capacity and in vivo functions. These findings demonstrate that the apoptotic death of Ag-specific T cell lines, cells which can be regarded as a model for memory T cells, can be prevented with IL-2. This effect may have important therapeutic implications for patients receiving chemotherapy or radiotherapy, and for patients with AIDS who develop immunodeficiency primarily as a result of loss of Ag-specific memory T cells.

Characterization of the complete genomic structure of the human WNT-5A gene, functional analysis of its promoter, chromosomal mapping, and expression in early human embryogenesis

We report the complete genomic organization of the human WNT-5A gene, which encodes a cysteine-rich growth factor involved in cell-cell signaling during growth and differentiation. The gene comprises five exons with the terminal exon coding for a large 3'-untranslated region of approximately 6.5 kilobase pairs and utilizes multiple polyadenylation signals to generate at least four discrete transcripts. We discovered a new leader exon interrupted by a 411-base pair intron that was retained in our original cDNA cloning. The promoter region was located in a GpC-rich island and harbored numerous cis-acting elements including several GC boxes and Sp1, AP1, and AP2 binding motifs. It lacked TATA or CAAT boxes typical of housekeeping and growth factor genes. In support of this, primer extension revealed extension two transcription start sites. Transient cell transfection assays showed functional promoter activity for the 3.9-kilobase pair 5'-flanking region. Interestingly, internal and 5' deletions revealed tha the distal promoter was not required for full transcriptional activity and that the first 631 base pairs of WNT-5A harbored the strongest promoter activity. Using a panel of rodent-human hybrid DNAs carrying portions of chromosome 3p, we mapped the gene to 3p14.2-p21.1, between a constitutional and a familial renal cell carcinoma-associated translocation. In situ hybridization analyses of early human embryos at 28-42 days of gestation revealed that WNT-5A transcripts were not restricted to the developing brain and limbs but were also observed in the mesenchyme bordering the pharyngeal clefts and pouches and in the developing gonads and kidneys. The relatively high expression in the celomic epithelium and in the precursors of follicles and seminiferous tubules suggest a novel role for WNT-5A in germ-cell differentiation. This study provides the molecular basis for discerning the regulation of the WNT-5A gene and offers the opportunity to investigate genetic disorders linked to this important gene.

Vaccines to prevent and treat autoimmune diseases

The current therapy for human autoimmune disease is based on nonselective immunosuppression achieved by corticosteroids or cytotoxic drugs. This form of therapy is toxic and frequently not effective in curing the disease. The study of experimental autoimmune disease models indicates that the pathogenic population of immune cells is restricted in terms of T-cell receptor gene usage and peptide epitopes recognized in the self-antigens. The recent developments in understanding of the pathophysiology of autoimmune disease point to the crucial role of the pathogenic T cell, the autoantigenic peptide, and the major histocompatibility complex molecules as well as the regulatory T-cell population in the disease process. The purpose of this review is to describe the use of vaccines to prevent and treat autoimmune disease. Encouraging results in animal models using vaccines based on the pathogenic T cell or the autoantigen have prompted the design of novel and selective immune-based therapies for human autoimmune disease.

Induction of diabetes in standard mice by immunization with the p277 peptide of a 60-kDa heat shock protein

We previously reported that immunity to the p277 peptide of the human 60-kDa heat shock protein (hsp60) was a causal factor in the diabetes of non-obese diabetic (NOD) mice, which are genetically prone to develop spontaneous autoimmune diabetes. The present study was done to test whether immunization with the p277 peptide could cause diabetes in standard strains of mice. We now report that a single administration of the p277 peptide conjugated to carrier molecules such as bovine serum albumin or ovalbumin can induce diabetes in C57BL/6 mice and in other strains not genetically prone to develop diabetes. The diabetes was marked by hyperglycemia, insulitis, insulin autoantibodies, glucose intolerance and low blood levels of insulin. The diabetes could be transferred to naive recipients by anti-p277 T cell lines. Similar to other experimentally induced autoimmune diseases, the autoimmune diabetes remitted spontaneously. After recovery, the mice were found to have acquired resistance to a second induction of diabetes. Susceptibility to induced diabetes in C57BL/6 mice was influenced by sex (males were much more susceptible than were females) and by class II genes in the major histocompatibility complex (B6.H-2bm12 mice with a mutation in the MHC-II molecule were relatively resistant). Other strains of mice susceptible to induced diabetes were C57BL/KSJ, C3HeB/FeJ, and NON/Lt. BALB/c and C3H/HeJ strains were relatively resistant. Immunization to p277-carrier conjugates could also induce transient hyperglycemia in young NOD mice, but upon recovery from the induced diabetes, the NOD mice were found to have acquired resistance to later development of spontaneous diabetes. Thus, T cell immunity to the p277 peptide can suffice to induce diabetes in standard mice, and a short bout of induced diabetes can affect the chronic process that would otherwise lead to spontaneous diabetes in diabetes-prone NOD mice.

Pathogenicity of T cells responsive to diverse cryptic epitopes of myelin basic protein in the Lewis rat

The cellular immunology of experimental autoimmune encephalomyelitis, a model for multiple sclerosis, has been studied, for the most part, using T cells directed to dominant epitopes of the Ag myelin basic protein (MBP). To characterize T cells reactive to cryptic epitopes of MBP, we immunized Lewis rats with each of 17 overlapping peptides of the 18.5-kDa isoform of rat MBP. We found that, in addition to the known 71-90 epitope, six other peptides induced active encephalomyelitis in the majority the injected rats. T cell lines raised to six different MBP epitopes were encephalitogenic upon adoptive transfer to naive rats. In contrast to the T cells specific for the dominant 71-90 peptide, the T cell lines reactive to cryptic epitopes were not restricted in their TCR genes to V beta 8.2, and some of the lines caused prolonged disease. Thus, T cells of different specificities and TCR usage can be pathogenic.

Pathogenicity of T cells responsive to diverse cryptic epitopes of myelin basic protein in the Lewis rat

The cellular immunology of experimental autoimmune encephalomyelitis, a model for multiple sclerosis, has been studied, for the most part, using T cells directed to dominant epitopes of the Ag myelin basic protein (MBP). To characterize T cells reactive to cryptic epitopes of MBP, we immunized Lewis rats with each of 17 overlapping peptides of the 18.5-kDa isoform of rat MBP. We found that, in addition to the known 71-90 epitope, six other peptides induced active encephalomyelitis in the majority the injected rats. T cell lines raised to six different MBP epitopes were encephalitogenic upon adoptive transfer to naive rats. In contrast to the T cells specific for the dominant 71-90 peptide, the T cell lines reactive to cryptic epitopes were not restricted in their TCR genes to V beta 8.2, and some of the lines caused prolonged disease. Thus, T cells of different specificities and TCR usage can be pathogenic.

Steroid treatment fails to induce an afternoon luteinizing hormone or prolactin surge in rats exposed to short-term constant light at the time of ovariectomy

The present study investigated the effects of short-term exposure to constant light, initiated at the time of ovariectomy, on the ability of estradiol (E2) treatment alone or in conjunction with progesterone (P) to induce afternoon surges of LH and prolactin (PRL). Adult Fischer 344 rats, which had been ovariectomized (OVX) and placed into constant light (LL) on day 0, were implanted with Silastic capsules containing E2 on day 7 and an atrial cannula on day 8. On the following day (day 9), hourly blood samples were collected between 12.00 and 20.00 h from LL-exposed animals which had received E2 treatment alone or from LL E2-treated animals which had also received P at 12.20 h. Blood samples from control animals which were OVX and treated with E2, but maintained under a 12-hour light:12-hour dark photoperiod, were also collected. Exposure to 9 days of LL abolished the ability of E2 treatment to induce an afternoon surge of LH or PRL. The addition of P treatment to LL E2-treated animals failed to reinstate an LH or PRL surge. While P treatment in LL E2-treated animals induced a rise in PRL levels, it is unlikely, given the timing, duration, and magnitude of PRL release, that this enhancement was initiated by the same mechanisms which normally generate the afternoon surge. The results from the present study demonstrate that short-term exposure to LL, initiated at the time of OVX, abolishes the E2-induced afternoon surges of LH and PRL.

Treatment of autoimmune diabetes and insulitis in NOD mice with heat shock protein 60 peptide p277

We recently showed that a peptide of the M(r) 60,000 heat shock protein molecule, designated peptide p277, is a target of T-cells in autoimmune diabetes in NOD mice. Indeed, the p277 peptide could be used as a therapeutic agent to arrest the autoimmune process even after it was far advanced. The present study was done to document the effects of p277 therapy on inflammation of the islets and on T-cell responsiveness to p277. Groups of female NOD mice of various ages up to 17 weeks were treated with a single inoculation of p277 given before or after the onset of overt hyperglycemia. We now report that fragments of p277 can affect diabetes but that optimal therapy requires the whole peptide. The positive response to p277 was dependent on administration of a threshold dose of peptide. Therapy was accompanied by the regression of intra-islet inflammation and the reappearance of histologically normal islets. Successful peptide therapy was associated with downregulation of T-cell immunity to p277. Adoptive transfer experiments demonstrated that the spleen cells of p277-treated mice were no longer diabetogenic and also could suppress the diabetogenic potential of cotransferred spleen cells of untreated female NOD mice. These results indicate that specific treatment of diabetes with a defined peptide can reprogram the autoimmune response.

Functional activation of encephalitogenic T cells in the absence of antigen-presenting cells

Co-stimulatory signals provided by surface receptors of antigen-presenting cells (APC) are crucial for the activation of CD4+ T cells, classically measured by cell proliferation or IL-2 secretion. The contribution of APC co-stimulatory signals to the acquisition of various effector functions by activated T cells is not fully understood. We have now examined the importance of surface-mediated co-stimulation by APC for activation of the effector potential of T cell clones mediating experimental allergic encephalomyelitis (EAE). We now report that T cell clones can be activated to produce EAE not only with APC but also by antibody-mediated TCR cross-linking in the presence of a mixture of T cell growth factors. Without activation, the T cell clones did not cause EAE. Therefore, at least some types of T cells can be activated to express their effector potential in the absence of any surface co-stimulatory signals requiring intact APC.

Self and foreign 60-kilodalton heat shock protein T cell epitope peptides serve as immunogenic carriers for a T cell-independent sugar antigen

Healthy individuals manifest natural T cell reactivity to epitopes of the 60-kDa heat shock protein (hsp60) of both self and bacterial origin. The present studies were done to learn whether defined peptides of hsp60 could function as T cell carrier epitopes for a poorly immunogenic T-independent capsular polysaccharide, the Vi Ag of Salmonella typhi. Homologous peptides were synthesized from the mouse self-hsp60 molecule (CP1m), from the closely related human hsp60 molecule (CP1h), and from the more distant Escherichia coli (CP1ec) and mycobacterial (CP1mt) hsp60 molecules. The peptides were conjugated to Vi and tested for their immunogenicity in BALB/c (H-2d) and H-2 congenic mice (H-2k and H-2b). We now report that the self-CP1m and cross-reactive CP1h peptides were as immunogenic as was the non-cross-reactive foreign CP1ec peptide. Small amounts of the CP1 peptide, even in PBS, sufficed to induce anti-Vi Abs of the IgG1 (T-dependent) isotype in naive mice. The carrier effect was associated with the ability of the peptides to bind to APC and to induce T cell proliferation. H-2d and H-2k mice, but not H-2b mice responded to CP1m/h and CP1ec. None of the mice responded to CP1mt. No signs of inflammation or autoimmune disease were detected. Thus, natural T cell autoimmunity exists and can be harnessed to provide T cell help for Ab production to a foreign bacterial molecule in a synthetic vaccine.

Self and foreign 60-kilodalton heat shock protein T cell epitope peptides serve as immunogenic carriers for a T cell-independent sugar antigen

Healthy individuals manifest natural T cell reactivity to epitopes of the 60-kDa heat shock protein (hsp60) of both self and bacterial origin. The present studies were done to learn whether defined peptides of hsp60 could function as T cell carrier epitopes for a poorly immunogenic T-independent capsular polysaccharide, the Vi Ag of Salmonella typhi. Homologous peptides were synthesized from the mouse self-hsp60 molecule (CP1m), from the closely related human hsp60 molecule (CP1h), and from the more distant Escherichia coli (CP1ec) and mycobacterial (CP1mt) hsp60 molecules. The peptides were conjugated to Vi and tested for their immunogenicity in BALB/c (H-2d) and H-2 congenic mice (H-2k and H-2b). We now report that the self-CP1m and cross-reactive CP1h peptides were as immunogenic as was the non-cross-reactive foreign CP1ec peptide. Small amounts of the CP1 peptide, even in PBS, sufficed to induce anti-Vi Abs of the IgG1 (T-dependent) isotype in naive mice. The carrier effect was associated with the ability of the peptides to bind to APC and to induce T cell proliferation. H-2d and H-2k mice, but not H-2b mice responded to CP1m/h and CP1ec. None of the mice responded to CP1mt. No signs of inflammation or autoimmune disease were detected. Thus, natural T cell autoimmunity exists and can be harnessed to provide T cell help for Ab production to a foreign bacterial molecule in a synthetic vaccine.

A disaccharide that inhibits tumor necrosis factor alpha is formed from the extracellular matrix by the enzyme heparanase

The activation of T cells by antigens or mitogens leads to the secretion of cytokines and enzymes that shape the inflammatory response. Among these molecular mediators of inflammation is a heparanase enzyme that degrades the heparan sulfate scaffold of the extracellular matrix (ECM). Activated T cells use heparanase to penetrate the ECM and gain access to the tissues. We now report that among the breakdown products of the ECM generated by heparanase is a trisulfated disaccharide that can inhibit delayed-type hypersensitivity (DTH) in mice. This inhibition of T-cell mediated inflammation in vivo was associated with an inhibitory effect of the disaccharide on the production of biologically active tumor necrosis factor alpha (TNF-alpha) by activated T cells in vitro; the trisulfated disaccharide did not affect T-cell viability or responsiveness generally. Both the in vivo and in vitro effects of the disaccharide manifested a bell-shaped dose-response curve. The inhibitory effects of the trisulfated disaccharide were lost if the sulfate groups were removed. Thus, the disaccharide, which may be a natural product of inflammation, can regulate the functional nature of the response by the T cell to activation. Such a feedback control mechanism could enable the T cell to assess the extent of tissue degradation and adjust its behavior accordingly.

The proteoglycan perlecan is expressed in the erythroleukemia cell line K562 and is upregulated by sodium butyrate and phorbol ester

Perlecan is a modular heparan sulfate proteoglycan that harbors five domains with homology to the low density lipoprotein receptor, epidermal growth factor, laminin and neural cell adhesion molecule. Using a monoclonal antibody directed against the laminin-like domain of perlecan, we have recently shown that perlecan is widely expressed in all lymphoreticular systems. To investigate further this observation we have studied the expression of perlecan in two human leukemic cell lines. Using reverse transcriptase-PCR, ribonuclease protection assay, and metabolic labeling we detected significant perlecan expression in the multipotential cell line K562, originally derived from a patient with chronic myelogenous leukemia. In contrast, the promyelocytic cell line HL-60 expressed perlecan at barely detectable levels. These results were intriguing because the K562 cells do not assemble or produce a classical basement membrane. Following induction with either sodium butyrate or the phorbol diester 12-0-tetradecanoylphorbol-13-acetate (TPA), K562 and HL-60 differentiate into early progenitor cells with erythroid or megakaryocytic properties, respectively. Following treatment of K562 and HL-60 cells with either of these agents, perlecan expression was markedly increased in K562 cells. In contrast, we could detect perlecan protein synthesis in HL-60 cells only at very low levels, even after induction with TPA or sodium butyrate. Collectively, these results indicate that perlecan is actively synthesized by bone marrow derived cells and suggest that this proteoglycan may play a role in hematopoietic cell differentiation.

A quantitative model of autoimmune disease and T-cell vaccination: does more mean less?

According to a simple mathematical model, the activated effector T cells that cause an autoimmune disorder can also cure the disease if administered in large doses. This prediction has been tested in the nonobese diabetic (NOD) mouse model and demonstrates that administration of intermediate doses of a diabetogenic T-cell clone caused early hyperglycemia, whereas a higher dose cured the disease. As discussed here by Lee Segel and colleagues, the proposed application of T-cell vaccination to treat clinical disease obliges immunologists to consider the quantitative complexities of regulation.