Biomedical subjects

A M Krensky

Publications and source records attributed to A M Krensky.

At least 73 records · Page 4Linked to original sources

PubMed1995

Novel tumor-associated accessory molecules involved in the gamma/delta cytotoxic T-lymphocyte-Burkitt's lymphoma interaction.

BACKGROUND: Tumor specific cytotoxic T lymphocytes (CTL) recognize antigen via the T-cell receptor (TCR). In addition, recognition requires accessory molecules involved in adhesion and signal transduction. The authors previously have characterized an autologous, Burkitt's lymphoma specific CTL line that uses the gamma-delta TCR to recognize antigen in a nonclassical context. The current study was undertaken to identify novel accessory molecules involved in this unusual TCR-tumor cell interaction. METHODS: A panel of monoclonal antibodies was generated against a Burkitt's lymphoma cell line and was screened for inhibition of autologous, tumor specific, cytolysis by a gamma-delta CTL line. Proteins identified by these monoclonal antibodies were further characterized by fluorescent-activated cell sorter analysis, Western blot and immunoprecipitation. RESULTS: Three known (CD5, CD43, and CD11a/CD18) and three novel (BAM-1, BAM-2, and BAM-3) cell surface molecules involved in the gamma-delta CTL-Burkitt's lymphoma interaction were identified and characterized. CONCLUSIONS: This study identifies and provides a preliminary characterization of three novel Burkitt's lymphoma-associated molecules involved in the gamma-delta CTL-tumor cell interaction and demonstrates that CD5, CD43, and CD11a/CD18 are involved in this interaction. It is likely that other unidentified accessory molecules are also involved in this and other effector cell-tumor interactions. Identification of such molecules may be useful in the design of new immunotherapeutic approaches.

Animals↗

PubMed1995

HLA-derived peptides as novel immunotherapeutics.

Soluble forms of HLA may be natural immunoregulatory molecules and may explain the "transfusion effect" seen in transplant patients in the precyclosporine era. Synthetic peptides corresponding to short linear sequences of HLA molecules have inhibitory effects on human T lymphocytes in vitro and cause tolerance induction in a rat heterotopic heart transplant model. Recent studies indicate that a subset of these peptides causes an increase in intracellular calcium which appears to account for T cell unresponsiveness and tolerance induction. The peptides bind to members of the heat-shock protein 70 family in a specific manner, depending upon peptide sequence. These studies provide a mechanism to explain the biologic activities of these new immunotherapeutic reagents.

Animals↗

PubMed1995

Immunosuppressive peptides corresponding to MHC class I sequences.

The induction of tolerance is a long-standing goal in transplantation. Intact MHC molecules, or fragments of them, are being used to render T cells unresponsive both in vitro and in vivo. Elucidation of the mechanisms underlying the effects of these treatments should aid the design of novel therapies for transplantation.

Crystallization↗

PubMed1995

HLA-derived peptides as novel immunosuppressives.

Peptides corresponding to linear sequences of HLA molecules have been synthesized and tested for immunomodulatory activity in in vitro assays using human T lymphocytes. Sequences from different parts of the HLA molecules have different effects. Peptides corresponding to residues 75-84 of an HLA class I supratypic specificity of limited heterogeneity (HLA-Bw4) had profound inhibitory effects in a variety of in vitro assays of human T lymphocyte function. Furthermore, a 2-wk course of human HLA sequences and cyclosporine therapy induced enduring immunologic tolerance in a rat model of heterotopic heart transplantation. These studies prompted clinical trials which are currently in progress. The peptides appear to induce T cell anergy by causing a prolonged intracellular calcium flux and interrupting normal signal transduction pathways. Furthermore, these peptides bind to members of the heat-shock protein 70 family, implicating these ubiquitous proteins in the immunomodulatory pathway. Such peptides may be normal physiologic mediators. In any case, they represent potential new immunotherapeutics for a variety of immune-mediated diseases.

Amino Acid Sequence↗

PubMed1995

Human leukocyte antigen-derived peptides as novel immunosuppressives.

Synthetic peptides corresponding to linear sequences of HLA class I and class II molecules can potently inhibit T lymphocytes responses both in vitro and in vivo. The class I and class II peptides studied to date seem to function by different mechanisms. Nevertheless, several different peptides have been shown to potently induce T cell anergy. Opelz and Terasaki first demonstrated that blood transfusions improved graft survival in transplant patients (19). Data from several sources indicate that blood transfusions are immunosuppressive in: 1) increasing infections in trauma patients who have received transfusions (20), 2) increasing metastases and/or relapses in cancer patients who have been transfused (21), and 3) remissions of autoimmune diseases associated with pregnancy and/or transfusion (22). It is likely that the active constituent of blood transfusions is soluble HLA molecule (23,24). Liver transplants, which are profoundly immunosuppressive in themselves, produce large amounts of soluble HLA (25). Both B and T lymphocytes in culture secrete soluble HLA (26). We hypothesize that soluble HLA is a natural immunoregulatory molecule involved in dampening of the immune response, but, even if this is not the case, synthetic peptides corresponding to HLA sequences have profound effects on T lymphocytes and may prove to be effective for the induction of clinical tolerance in transplant patients.

Animals↗

PubMed1994

Peptides corresponding to the CD8 and CD4 binding domains of HLA molecules block T lymphocyte immune responses in vitro.

CD4 and CD8 are cell surface glycoproteins that serve as co-receptors for Ag with the TCR. Recent studies have shown that both CD4 and CD8 interact with conserved regions of MHC class II and class I, respectively. To investigate further the roles of CD4 and CD8 in the immune response, we prepared synthetic peptides corresponding to the HLA sequences with which CD4 and CD8 are thought to interact. The peptide corresponding to residues 222 to 235 of the HLA class I heavy chain blocked the differentiation of human CTL precursors into active effect cells but affected neither the ability of PBLs to proliferate in response to mitogen nor the cytotoxic activity of established CTLs. In contrast, the peptide corresponding to residues 134 to 152 of the HLA-DR beta-chain inhibited the differentiation of CTL precursors, the proliferative response of freshly isolated PBL, and the proliferation of an established alloreactive CD4+ T cell clone to Ag. The inhibitory effect of the DR.134-152 peptide on CTL differentiation could be overcome by addition of exogenous IL-2 to the limiting dilution cultures, whereas the effect of the HLA-1.222-235 peptide was unaffected by exogenous IL-2. These results directly demonstrate a functional role for these regions of MHC molecules and underscore the central role of both CD4 and CD8 in the effective initiation of a CTL response.

Base Sequence↗

PubMed1994

Induction of allograft tolerance in rats by an HLA class-I-derived peptide and cyclosporine A.

T cell recognition of MHC molecules initiates a cascade of events resulting in allograft rejection. CTLs damage the graft by targeting nonself-MHC class I molecules. We and others have previously shown that small synthetic peptides corresponding to regions of certain MHC class I molecules can inhibit the CTL response against MHC class I alloantigens in vitro. Here we report that rat heart allografts survived survived indefinitely when transplanted into recipients treated with a synthetic peptide corresponding to residues 75-84 of (B7.75-84) in combination with a subtherapeutic dose of cyclosporine A. Furthermore, this treatment induced long-term donor-specific tolerance that was mediated by anergic cells, indicating that such peptides may have potential as therapeutics for human organ transplantation.

Amino Acid Sequence↗

PubMed1994

RANTES chemokine expression in cell-mediated transplant rejection of the kidney.

RANTES (regulated upon activation, normal T cell expressed and secreted) is a chemotactic cytokine (a chemokine) for memory T lymphocytes, monocytes, and eosinophils. RANTES expression was studied in renal allograft biopsy specimens. Although RANTES was not expressed in samples taken one hour after transplantation, or in native renal biopsy specimens from patients with cyclosporin nephrotoxicity, it was expressed during cell-mediated transplant rejection. RANTES mRNA was detected in infiltrating mononuclear cells and renal tubular epithelium, and RANTES protein was localised to mononuclear cells, tubular epithelium, and vascular endothelium. This suggests RANTES has a role in allograft rejection.

Biopsy↗

PubMed1994

Prospects for induction of tolerance in renal transplantation.

Immunological tolerance is the ultimate goal of transplantation immunobiology. Current therapies involve nonspecific immunosuppression with concomitant risks for infection, malignancy, and drug-specific side effects. By inducing specific immune unresponsiveness to the graft it should be possible to maintain transplants without the need for chronic drug administration and without the risk of nonspecific immunosuppression. This review highlights recent progress in the understanding of immunological tolerance, with special attention to the long-term prospects for successful induction of tolerance in renal transplant patients.

Age Factors↗

PubMed1994

The induction of tolerance to alloantigens using HLA-based synthetic peptides.

The identification of immunomodulatory approaches that allow the induction of antigen-specific unresponsiveness is required for long-term graft survival without the complications of chronic immunosuppression. Recent novel strategies based upon treatment with synthetic peptides corresponding to linear sequences of MHC class I and II molecules reproducibly induce tolerance to alloantigens. Although the mechanisms involved are still not completely understood, the phenomenology reported makes these approaches promising for evaluation in clinical trials.

Animals↗

PubMed1994

Transplantation immunology.

A major function of the immune response is the discrimination of self from nonself. It is this response that must be overcome in transplant rejection. Progress in understanding these basic immune mechanisms has helped to improve clinical outcome and lays the foundation for a new generation of therapies.

Graft Rejection↗

PubMed1994

T cells in autoimmunity and allograft rejection.

Since T lymphocytes are important regulators and effectors of the immune response, a basic understanding of T lymphocyte activation and differentiation may lay the basis for novel immunotherapies of immune mediated diseases. Potential sites at which to interrupt T lymphocyte mediated diseases include: (1) HLA-peptide interactions, (2) T cell receptor (TCR) recognition of peptides in the context of HLA, (3) biochemical signals mediated via the TCR, (4) numerous other cellular adhesion and signaling pathways, (5) second messengers, (6) transcription factors, and (7) various effector molecules, including granzymes and perforin. We have investigated the effects of peptides corresponding to linear sequences of HLA class I molecules. Previously, we showed that peptides corresponding to regions of the polymorphic alpha 1 and alpha 2 domains could inhibit lysis by cytotoxic T lymphocytes (CTL) specific for those regions. We now show that peptides corresponding to certain conserved regions of the HLA class I molecule can profoundly inhibit CTL. Furthermore, peptides corresponding to a particular conserved region of the HLA class I alpha 1 alpha helix are able to significantly prolong rat heterotopic heart transplants when given in conjunction with a sub-therapeutic course of cyclosporin A. These observations raise the possibility that soluble HLA molecules are natural immunoregulatory factors in vivo and that synthetic peptides may prove useful as novel immunosuppressive drugs.

Amino Acid Sequence↗

PubMed1993

Monocyte haptotaxis induced by the RANTES chemokine.

BACKGROUND: Soluble mediators and inducible cell-surface molecules coordinate the ordered cascade of events giving rise to inflammation. The specific mechanisms underlying the attraction of antigen-specific cells into a site of inflammation remain sketchy, however. In particular, it is unclear how chemoattractants cause rapidly moving immune cells to adhere to the blood vessel wall and to enter inflamed tissues. RESULTS: Here we show that RANTES, a potent chemo-attractant for monocytes and T lymphocytes, is inducibly expressed within an inflamed organ, binds to endothelial cells, and promotes haptotaxis, the migration of cells induced by surface-bound gradients. CONCLUSION: These findings lead us to propose a model for the role of RANTES in the migration of antigen-specific immune cells into an inflammatory site.

Journal Article↗

PubMed1993

Genomic organization and transcriptional regulation of the RANTES chemokine gene.

RANTES is a member of a large supergene family of pro-inflammatory cytokines called CC chemokines that appear to play a fundamental role in inflammatory processes. The RANTES protein causes release of histamine from basophils and is a chemoattractant for CD45RO/CD4+ "memory" T lymphocytes, monocytes, and eosinophils. Although expression of RANTES was first thought to be limited to activated T cells, recent data have shown that it is produced by a variety of tissue types in response to specific stimuli. RANTES mRNA is expressed late (3 to 5 days) after activation of resting T cells whereas in fibroblasts, renal epithelial and mesangial cells, RANTES mRNA is quickly up-regulated by TNF-alpha stimulation. In order to gain a better understanding of the molecular mechanisms that regulate expression of the RANTES locus, we have characterized the RANTES gene and determined a putative promoter region. The RANTES gene spans approximately 7.1 kb and is composed of three exons of 133, 112 and 1075 bases and two introns of approximately 1.4 and 4.4 kb with the position of intron/exon boundaries conserved relative to the other CC chemokine family members. Approximately 1 kb of DNA from the immediate 5' upstream region of RANTES was sequenced and found to contain a large number of potential consensus elements for specific T cell/hemopoietic, myeloid, muscle, and ubiquitously expressed DNA-binding factors. RANTES-promoter-luciferase gene fusion assays demonstrate high levels of reporter gene activity in a "mature" T cell line Hut78, the erythroleukemic cell line HEL, and the rhabdomyosarcoma cell line RD, with little or no activity in the "early" T cell line Jurkat, the gamma delta T cell line PEER, the thymic tumor Molt4, or the pre-erythroid cell line K562. Deletion analysis of the promoter region indicates that different transcriptional mechanisms control expression of RANTES in the various tissues studied.

Base Sequence↗

PubMed1993

Insulin-like growth factor binding protein-3 protease activity in the urine of children with chronic renal failure.

The insulin-like growth factors, IGF-1 and IGF-II, are polypeptides that potentiate cellular growth. In addition to binding to specific cell surface receptors, the IGFs bind with high affinity to a family of proteins, the insulin-like growth factor binding proteins (IGFBPs). Serum and urine IGFBP patterns are altered in individuals with chronic renal failure (CRF). We recently reported that the urinary IGFBP pattern of CRF patients is unique for increased insulin-like growth factor binding protein-1 (U-IGFBP-1) levels. In this study, we used western ligand blotting (WLB), western immunoblotting (WIB), and radioimmunoassay (RIA) to further evaluate serum and urine IGFBP profiles of children with CRF (n = 14). Five patients with CRF displayed decreased serum IGFBP-3 profiles by WLB. Serum IGFBP-3 WIB profiles were remarkable for 30- and 20-kDa fragments of IGFBP-3 not seen in control serum. Serum IGFBP-3 levels, as determined by RIA, were slightly elevated. Serum levels of IGFBP-2 also were increased, although not at a level reaching statistical significance. WLB of CRF urine revealed a large increase in U-IGFBP-1 and a complete absence of urinary IGFBP-3. Recent studies of serum from pregnant women and seminal plasma have demonstrated a similar absence of intact IGFBP-3, due to the presence of a specific IGFBP-3 protease. To evaluate whether an IGFBP-3 protease accounts for the absence of intact U-IGFBP-3 in children with CRF, urine and serum samples from individuals with CRF and controls were tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1993

The CD8 coreceptor interaction with the alpha 3 domain of HLA class I is critical to the differentiation of human cytotoxic T-lymphocytes specific for HLA-A2 and HLA-Cw4.

The CD8 coreceptor interacts with MHC class I molecules through an acidic loop in the MHC alpha 3 domain. Mutations in this region reduced binding between cells expressing mutant HLA molecules and CHO cells transfected with CD8 alpha chain, with mutations at residue 227 having the greatest effects. This study was undertaken to examine the role of the CD8-HLA interaction in the generation of primary and long-term CTLs. HLA-A*0201 genes (wild type or mutated at residue 227) were transfected into a cell line that lacked expression of HLA-A or B molecules but expressed HLA-Cw4. These cells were used as stimulators for PBLs from a normal donor. Cultures were tested for cytotoxicity at various times thereafter. Transfectants expressing the HLA-A*0201 mutant gene were poor stimulators of primary HLA-A2-specific CTLs. In long-term culture, HLA-Cw4-specific CTLs predominated, indicating that continuous expansion of allogeneic CTLs depends upon an efficient CD8-MHC class I interaction.

CD8 Antigens↗

PubMed1993

TNF alpha induces expression of the chemoattractant cytokine RANTES in cultured mouse mesangial cells.

We investigated the effect of several immune-relevant cytokines on expression of the chemoattractant intercrine/chemokine RANTES in a mouse mesangial cell line (MMC). Fifty ng/ml recombinant tumor necrosis factor alpha (TNF alpha) induced a marked increase in RANTES transcripts after two hours. RANTES mRNA remained elevated for 24 to 48 hours after stimulation, and could be abolished by co-incubation with 30 micrograms/ml of a neutralizing rabbit anti-TNF alpha antibody. Protein expression of RANTES, as assessed by indirect immunofluorescence and Western blotting, increased in MMCs 24 hours after TNF alpha stimulation. Interleukin-1 beta, tumor necrosis factor beta (TNF beta), and lipopolysaccharide (LPS) also increased expression of RANTES mRNA. In addition, RANTES mRNA expression was stimulated in glomeruli harvested from rats following renal in vivo perfusion with TNF alpha. Our results indicate that mesangial cells produce the small cytokine RANTES. This factor, in concert with other chemoattractants, may play a role in the glomerular recruitment of inflammatory cells like macrophages/monocytes.

Animals↗

PubMed1993

The nature of allorecognition.

Understanding the nature of allorecognition is fundamental to the design of antigen-specific therapies for transplantation. As recently as 10 years ago it was generally believed that recognition of major histocompatibility complex (MHC) molecules by T lymphocytes was direct and represented the "simplest" kind of T-lymphocyte interaction. It is now clear that the nature of allorecognition is complex, involving a variety of different forms of MHC antigens with or without peptides contained in their antigen-binding groove. In addition, there is renewed interest in alternative forms of allorecognition, including so-called indirect allorecognition, in which donor alloantigens are recognized as peptides in the context of recipient self. Lastly, it appears that cells other than T lymphocytes, eg, natural killer cells, are capable of antigen-specific recognition and may be responsible for heretofore underappreciated mechanisms of transplant rejection.

Histocompatibility Antigens Class I↗