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N Zavazava

Publications and source records attributed to N Zavazava.

At least 19 recordsLinked to original sources
PubMed2001

Donor-derived soluble MHC antigens plus low-dose cyclosporine induce transplantation unresponsiveness independent of the thymus by down-regulating T cell-mediated alloresponses in a rat transplantation model.

BACKGROUND: In vitro, soluble MHC (sMHC) antigens modulate and induce apoptosis in alloreactive and antigen-specific T cells, demonstrating their potency to regulate T cell-mediated immune responses. However, their efficacy to regulate immunological responses in vivo remains unclear. Here, we report that repetitive intraperitoneal injection of recombinant Lewis rat-derived MHC class I antigens in Dark Agouti (DA) rats modulates alloreactivity. METHODS: RT1.A1 (Lewis derived) genes were cloned into mammalian expression vectors, and RT1.Aa (DA derived) genes were used to transfect a rat myeloma cell line. RT1.A1 molecules were injected intraperitoneally in DA recipients that subsequently underwent transplantation with Lewis-derived cardiac allografts. RESULTS: Soluble class I antigens were secreted by the transfected cells and were shown to be heterodimeric, peptide-loaded, and conformationally folded. Injection of donor-derived soluble MHC significantly reduced the ability of recipient animals to mount a cytotoxic T-cell response to donor-derived tissue. More interestingly, this treatment significantly prolonged donor-graft survival and allowed 60% of treated animals to develop graft tolerance (>120 days), when donor sMHC were combined with a single subtherapeutic dosage of cyclosporine. Thymectomy of recipient animals before transplantation did not interfere with induction of peripheral tolerance. CONCLUSIONS: Donor-derived sMHC are potential tolerogens for down-regulating the cytotoxic T-cell response of animals that undergo transplantation. Thus, these data provide for the first time a rationale for the application of directly injected sMHC in vivo to down-regulate immunological responses and aid the induction of graft tolerance.

Animals↗
PubMed2001

Allogeneic recombinant soluble MHC class I molecules modify urinary odor cues in rats.

The highly polymorphic genes of the major histocompatibility complex (MHC) determine, in part, the odor cues and behavior of an individual. In animal models, MHC-associated odors that regulate distinct behavior have been identified mainly in urine. However, the underlying mechanism is still not clear. Here, we show that injected recombinant soluble (rs) MHC class I molecules (DA, rsRT1.A(a) and Lewis, rsRT1.A(l)) temporarily alter urine odor of Lewis test rats (RT1.A(l)). This change in urinary signals was observed in behavioral assays using the habituation/dishabituation test and in odor signals analysed by gas chromatography (GC) and mass spectrometry (MS). Gas chromatographic analysis revealed that these altered odor signals are caused by quantitative changes of at least two nitrogen-containing urinary compounds. The results suggest that urinary olfactory cues are directly or indirectly influenced by MHC class I gene products.

Animals↗
PubMed2000

Co-transplantation of donor-derived hepatocytes induces long-term tolerance to cardiac allografts in a rat model.

BACKGROUND: Liver allografts transplanted between MHC-disparate mice, rats, and swine are spontaneously accepted in most strain combinations without requirement for immunosuppression. The underlying mechanism has, however, remained elusive. Here, we demonstrate that co-transplantation of donor-derived hepatocytes protect Lewis (RT1.A1) cardiac allografts from acute and chronic rejection in DA (RT1.Aa) recipients indefinitely. METHODS: Livers of donor Lewis rats were harvested and the hepatocytes separated from hepatic leukocytes by collagenase digestion and gradient separation. DA recipient animals were transplanted Lewis cardiac allografts and simultaneously intraportally infused either Lewis-derived hepatocytes or hepatic leukocytes. Recipient animals were either not further treated or received a single dose of 15 mg/kg cyclosporine. RESULTS: Donor hepatocytes alone significantly protected syngeneic cardiac allografts from rejection, whereas hepatic leukocytes failed to influence graft survival. In combination with cyclosporine, recipient cardiac allografts were indefinitely protected from rejection. Graft-infiltrating cells in tolerant animals presented as clusters of CD4+ T cells and stained mostly positive for interleukin-4, whereas graft-infiltrating cells in rejected allografts were predominantly positive for interferon-gamma. Adoptive transfer of splenocytes derived from tolerant animals protected Lewis cardiac allografts from rejection in DA recipients without immunosuppression. In contrast, hepatic leukocytes protected only 50% of the allografts from rejection. CONCLUSION: We propose that donor hepatocytes induce permanent engraftment of syngeneic allografts by establishing a Th2 type alloresponse that is transferable to new graft recipients. The results of this study demonstrate that liver parenchymal cells significantly mediate spontaneously liver-induced tolerance.

Adoptive Transfer↗
PubMed2000

Oral feeding of an immunodominant MHC donor-derived synthetic class I peptide prolongs graft survival of heterotopic cardiac allografts in a high-responder rat strain combination.

The efficacy of two synthetic major histocompatibility complex (MHC)-derived DA (RT1.Aa) 25-mer peptides (residues 56-80 and 96-120) to modulate alloreactivity was tested in Lewis (RT1.A1) responder animals. The DA peptide 56-80, but not peptide 96-120, induced delayed-type hypersensitivity (DTH). DTH was significantly reduced by oral feeding of peptide 56-80, P = 0.004. In addition, oral feeding of this peptide in combination with a short course of cyclosporin A (CsA) prolonged graft survival of 60% of heterotope transplanted DA cardiac allografts in Lewis recipient rats. Long-term survivors developed low levels of allo-antibodies against donor tissue as compared to rejecting animals and increased levels of interleukin-4 (IL-4) within the allograft. Similarly, IL-4-secreting splenocytes were identified by flow cytometry in these animals, indicating a Th2-type cytokine pattern. However, graft survival was particularly limited to cardiac allografts because donor-type skin grafts were acutely rejected in tolerant animals. It is interesting that residue alignment of peptide 56-80 to the motif of the RT1.A1 molecule showed a preferred class I motif within this sequence, suggesting indirect presentation of this peptide to recipient T cells. Thus, peptide 56-80 appears to represent a dominant epitope that can be exploited for establishing tolerance in this transplantation strain combination.

Administration, Oral↗
PubMed2000

Synthetic HLA-A2 derived peptides are recognized and presented in renal graft recipients.

Indirect presentation of allogeneic MHC antigen is an important pathway by which allografts are rejected and tolerance maintained by regulatory CD4(+) T cells. In this study HLA-A2 derived synthetic peptides were used to determine whether T cells of non-HLA-A2 renal graft recipients, which had been HLA-A2 mismatched to their organ donors, recognize some of the HLA-A2-derived peptides. Among the HLA-A2 mismatched patients, 60% recognized residues 56--69, 65--79, and 75--89. Peripheral blood lymphocytes derived from healthy individuals showed low reactivity towards allopeptides, indicating that sensitization towards HLA-A2 induced response towards HLA-A2 derived peptides. The response to the peptides was blocked by antibodies to HLA-DR, -DQ, and CD4. Depletion of antigen presenting cells abrogated response towards the allopeptides, confirming that the observed proliferation was mediated by the indirect pathway. Interestingly, although none of the HLA-A2 mismatched patients had any signs for either acute or chronic rejection, considerable response to allo-derived HLA-A2 was observed.

Amino Acid Sequence↗
PubMed2000

HLA-G has a concentration-dependent effect on the generation of an allo-CTL response.

Human leucocyte antigen (HLA) -G is expressed on trophoblast cells during pregnancy, suggesting a role in protection of the semiallogeneic fetus. Published data suggest that HLA-G protects a cell against natural killer cell lysis. It has been hypothesized that HLA-G may also protect the fetus by preventing allo-cytotoxic T lymphocyte (CTL) responses. To test this hypothesis, we assayed the effects of various concentrations of purified HLA-G on CTL response in a mixed lymphocyte culture (MLC) system. We found that concentrations > or =0.1 microg/ml of HLA-G suppressed the allo-CTL response by 30-100% over the control, but, paradoxically, concentrations of 0.01-0.05 microg/ml of HLA-G augmented the allo-CTL response by 25-50% over the control. Concentrations < or = 0.001 microg/ml HLA-G had no effect. Addition of HLA-G to preprimed allo-CTL effector cells did not affect their killing ability. Allo-CTL suppressive doses of HLA-G induced a T helper type 2 (Th2) cytokine response, whereas allo-CTL-enhancing doses of HLA-G induced a Th1-type cytokine response. HLA-G purified from first-trimester placenta does not affect allo-proliferative responses nor does it alter the percentage of CD4+ or CD8+ T cells in MLCs. These findings support a potential role for HLA-G-mediated suppression of allo-CTL formation in normal pregnancies. In addition, the effects observed at lower concentrations of HLA-G may have interesting implications for the condition of pre-eclampsia in which concentrations of this HLA class I molecule are reduced.

Antibodies, Monoclonal↗
PubMed2000

Alloreactivity and apoptosis in graft rejection and transplantation tolerance.

Weissmann wrote as early as 1889 that higher organisms contain within themselves the germs of death [1]. However, the term, programmed cell death, or apoptosis as it is now known, was defined much later [2]. Thus, it was long recognized that damaged and old cells are eliminated within the body, but the underlying mechanisms are only now beginning to emerge. Apoptosis appears central to the process of negative selection of developing T-cells in the thymus. In regard to organ transplantation, apoptosis contributes to graft rejection and the establishment of graft tolerance. Thus, understanding the regulatory mechanisms of apoptosis may help establish a new protocol for the induction of transplantation tolerance.

Animals↗
PubMed1999

Different in vivo tolerogenicity of MHC class I peptides.

The efficacy of MHC class I-derived peptides to induce tolerance was tested in a cardiac transplantation model. Two 25-mer peptides from the polymorphic region of the DA class I molecule (RT1.Aa) were synthesized by F-moc chemistry and injected intrathymically or intraperitoneally into LEW (RT1.1) responder animals. Intrathymic treatment of the recipient animals with peptide 1 (residues 56-80) accompanied by intraperitoneal treatment with peptide 4 (residues 96-120) led to indefinite survival of allogeneic DA cardiac allografts (n = 7; > 100 days). The tolerogenicity of both peptides differed according to the site of inoculation, as donor-specific tolerance was only observed after administration of peptide 1 into the thymus and injection of peptide 2 into the abdominal cavity of LEW recipients, but not vice versa. Donor-specific tolerance was confirmed in vivo by grafting of full-thickness skin and in vitro by appropriate proliferation and cytotoxicity assays using donor and third-party rats. Donor-specific tolerance was associated with up-regulation of interleukin-4, transforming growth factor beta, and interleukin-10 gene expression within cardiac allografts, thus suggesting intrathymic clonal deletion and external suppression with expansion of T-helper 2-type lymphocytes as the underlying mechanisms of tolerance induction.

Animals↗
PubMed1999

The role of natural killer cell mediated caspases activation in a graft-versus-host disease model of semiallogeneic small bowel transplantation.

In the clinical setting of solid organ transplantation the event of graft-versus-host disease (GvHD) is rare and not easily predictable. Even intestinal and multivisceral transplants harbour a huge amount of immunocompetent cells and they do not exert a significantly higher risk to trigger serious GvH reactions. A series of our own experimental studies has been conducted to delineate the role of the host's innate immune system in the context of GvHD following parental to F1 hybrid semiallogeneic small bowel transplantation (SBTx). These results clearly demonstrated the immunological significance of the recipient's status of natural killer (NK) cell activity to counteract donor-derived lymphocytes and related cytotoxicity. NK cells and macrophages are both endowed with Ca2+-dependent receptors of the C-type lectin family which interact with a diversity of high-affinity oligosaccharide ligands expressed on potential target cells. One of these proteins of the C-type lectin family, termed NKR-P1, has been cloned and sequenced. Activation of NKR-P1 stimulates activation-induced cell death (AICD) of bound target cells. As intracellular mediators of apoptotic cell death a new family of cysteine proteases, the caspases, have been defined. These proteases appear to be involved in the initiation of apoptosis in response to a number of stimuli. This study was conducted to investigate the impact on the activity level of host NK cells and on target cell lysis of donor-derived lymphocytes after heterotopic semiallogeneic (parental [DA;RT1.aaav1] to F1 [DA x LEW;RT1.(1)]) small bowel transplantation using a rat model. The host's NK activity was either specifically activated (by use of polyinosinic:polycytodilic acid [poly-I:C]) or suppressed (by depletion of host NK cells after intraperitoneal administration of the NKR-P1 monoclonal antibody 3.2.3). The impact of NK-activity on the incidence of GvHD and the recipients' survival was correlated with the frequency of apoptotic cell death and related expression of caspases 1 (ICE) and 3 (CPP-32) from donor and recipient small bowel tissues. Our results confirm that depletion of NK cells in F1 host rats prior to parental small bowel transplantation significantly decreased the mean survival to 11.4 days versus 16.2 days of nondepleted F1 rats (p < 0.01). Conversely, activation of host NK activity with poly-I:C abrogated GvHD in all 12 recipient rats and led to long-term survival in seven of 12 animals. Long-term survival was associated with a substantially higher frequency of apoptotic cell death in donor and recipient small bowel and mesenteric lymph nodes. On day 10 after transplantation, Northern blot analysis of these tissues revealed profound upregulation of mRNA-specific gene expression for caspase 1 and 3 as potential mediators of programmed cell death of activated lymphocytes. Our findings emphasize the importance of NK cell associated innate immunity in the context of GvHD after semiallogeneic small bowel transplantation. Killing of alloreactive donor-derived lymphocytes was mediated by the NKR-P1 protein on NK cells and could be suppressed after pretreatment of F1 hosts with anti-NKR-P1 mAb 3.2.3. Moreover, NK cell-mediated apoptosis induced upregulation of caspases 1 and 3, thus elucidating the involvement of this protein in the context of caspase-mediated target cell killing.

Animals↗
PubMed1999

How does the major histocompatibility complex influence behavior?

The major histocompatibility complex (MHC) encodes highly polymorphic cell surface glycoproteins that form the basis of immunological individuality. It has been postulated that MHC besides its role in immune defence also determines behavior through formation of specific odor cues. In addition several studies have implicated MHC disassortative odor and mating preferences in mice, rats, and humans. Further leading studies have suggested that mice and humans prefer to mate with MHC dissimilar individuals. Although the latter remains controversial, MHC dependent mating preferences provide a potentially important selective factor driving the polymorphisms of the MHC genes. Here we review some of the available data and hypotheses on the influence of the MHC on behavior and discuss its molecular and chemical basis.

Animals↗
PubMed1998

Purified truncated recombinant HLA-B7 molecules abrogate cell function in alloreactive cytotoxic T lymphocytes by apoptosis induction.

BACKGROUND: Soluble MHC class I molecules are ubiquitous in human body fluids, including serum, urine, sweat, and cerebrospinal fluid. However, their biological function has remained unresolved. Membrane-derived human soluble MHC molecules (soluble human leukocyte antigen; sHLA) have been shown to induce apoptosis in alloreactive cytotoxic T lymphocytes (CTL). Here we report the efficacy of recombinant soluble HLA-B7 (rsHLA-B7) to modulate T-cell function. METHODS: Primers of HLA-B7 were designed to allow amplification of a cDNA lacking the transmembrane and cytoplasmic domains yielding a truncated gene. rsHLA-B7 molecules were expressed in the human myeloma cell line 721.221 and purified by affinity chromatography using the BB7.7 mouse monoclonal antibody. CTL were generated from peripheral blood lymphocytes derived from healthy blood donors by stimulation with irradiated Epstein Barr virus-transformed HLA-B7-positive B cells. CTL were preincubated with rsHLA-B7, and cytotoxicity and apoptosis were tested according to standard procedure. RESULTS: A total of 2 x 10(6) cells/ml secreted 10 microg/ml rsHLA-B7 as determined by a conformation-dependent ELISA, suggesting that rsHLA-B7 do not require the transmembrane and cytoplasmic regions for proper folding. After purification by affinity chromatography, rsHLA-B7 induced apoptosis in anti-HLA-B7 CTL, but not in anti-HLA-A2-specific, CTL. As a consequence, allorecognition of target cells by the CTL was significantly blocked. CONCLUSION: Recombinant sHLA are sufficient binding cues for T cells, which efficiently induce apoptosis and block allorecognition of target cells by CTL. Thus, recombinant sHLA molecules may become a valuable new modality for specific immunological therapeutic intervention.

Animals↗
PubMed1998

WOFIE augments the immunosuppressive potency of FK-506. Window of opportunity for immunological engagement.

UNLABELLED: Bidirectional recognition of donor- and recipient-derived immunocompetent cells has been proven to play a pivotal role for the induction of long-term unresponsiveness to allogeneic grafts. This study investigated the fate of heterotopic heart grafts with respect to the timing of subtherapeutic doses of FK-506 and with respect to the time point and type of donor antigen application, leaving space for mutual adaptation of alloreactive lymphocytes, designated as the 'WOFIE-concept' (window of opportunity for immunological engagement), originally described by R Calne. METHODS: Heterotropic heart transplantation was performed using male DA (RT1.a) donor and LEW (RT1.1) recipient rats in the following groups (n = 6). FK-506 was applied intramuscularly (i.m.) using doses of 2 mg/kg x body weight per day. Donor antigen application was performed either by DA blood transfusion, 2 ml intravenously (i.v.), or by i.v. transfusion of 5 x 10(7) DA splenocytes. (i) LEW --> LEW, untreated; (ii) DA --> LEW, untreated; (iii) DA --> LEW, FK-506 days 0, 4-7; (iv) DA --> LEW, FK-506 as group (iii) plus 2 ml of DA blood 6 h post-Tx; (v) same as group (iv) but DA blood transfusion 24 h post-Tx; (vi) DA --> LEW, FK-506 as group (iii) plus DA splenocytes 6 h post-Tx; (vii) same as group (vi) but DA splenocyte transfusion 24 h post-Tx; (viii) DA --> LEW, FK-506 days 0-4 and (ix) DA --> LEW, FK-506 as group (viii) plus DA blood 6 h post-Tx. Immunohistochemical stainings (APAAP-method) of the allografts and flow cytometric analysis of recipient spleens were performed electively 3, 7 and 14 days after organ reperfusion. RESULTS: The mean graft survival differed significantly between groups and comprised (mean +/- SD days): (i) >100, (ii) 6.5 +/- 1.0, (iii) 31.6 +/- 12.1, (iv) 44.8 +/- 10.1, (v) 29.8 +/- 14.2, (vi) 27.2 +/- 4.7, (vii) 14.6 +/- 4.2, 17.5 +/- 4.2, (viii) 17.5 +/- 4.2 and (ix) 18.8 +/- 2.8 days. Prolongation of graft survival and long-term unresponsiveness (group iv) revealed a substantially different pattern of graft infiltration. CONCLUSIONS: Effective treatment with unspecific immunosuppressants like FK-506 can be substantially improved if (i) mutual antigen recognition between donor and recipient immunocompetent cells is warranted, (ii) donor-derived blood-borne antigens are given immediately after graft reperfusion, and (iii) the type of inoculated donor antigen has a strong impact on graft survival as splenocytes which contain a large population of professional antigen-presenting cells failed to prolong graft survival after interrupted FK-506 treatment.

Animals↗
PubMed1998

Soluble HLA class I molecules: biological significance and clinical implications.

Soluble class I human leukocyte antigens (sHLAs) have been detected in serum, sweat, lymphatic fluid, urine and cerebrospinal fluid. Their biological function has, however, remained a puzzle. The physiological concentration of sHLA varies more than tenfold depending on the phenotype of the individual, and is significantly upregulated in various diseases and during inflammation. This suggests that sHLAs might serve as a marker of pathological changes. Recent experiments have shown that, in vitro, sHLAs can modulate T-cell reactivity and induce cell-activated apoptosis, implicating sHLAs in the induction and maintenance of peripheral tolerance. Therefore, sHLAs have the therapeutic potential to induce tolerance to transplants.

Animals↗
PubMed1997

MHC and behavior.

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Behavior↗
PubMed1996

Circumvention of natural killer cell and T-cell mediated allogeneic target killing with tacrolimus (FK506) in small bowel transplantation related graft-vs-host disease.

The role of simultaneous donor-specific transfusion of unprocessed cellular bone marrow (BM) together with solid organ transplantation, a postulated concept to achieve long-term graft acceptance, was investigated in an experimental setting of semiallogeneic transplantation of parental small bowel (SBTx) to F1 hybrids. The established graft-vs-host (GvH) model revealed that simultaneous transfer of SB/BM substantially enhanced GvH-mediated immune responses in recipient target organs, e.g. skin, gut, and liver. In comparison to isolated SBTx, animal survival decreased from 16.1 (+/- 0.9) to 10.1 (+/- 0.8) days after additional BM transfusion, P < 0.001. Severe tissue injury of GvH-susceptible target organs in the setting of simultaneous SB and BMTx was associated with significant changes in recruitment and tissue distribution of NKR-P1+ cells during the GvH-related proliferative immune response. Tacrolimus effectively suppressed these initial events and prevented recipient animals from clinically and histologically observed damage caused by GvH disease.

Animals↗
PubMed1996

In vivo depletion of NKR-P1 positive cells in the recipient prior to small bowel transplantation enhances graft-versus-host disease (GvHD) in the rat.

Recent evidence for major histocompatibility complex (MHC) class I antigen-directed recognition mechanisms of natural killer cells (NKs) have revived interests in investigating non-adaptive immune responses in the framework of solid organ transplantation. A semi-allogeneic rat model of heterotopic small bowel transplantation (HSBTx) from male DA parental to male F1 hybrid rats (DA x LEW) was established to investigate the role of host NKs to attenuate graft-versus-host (GvH)-mediated immunosuppression and tissue injury. By use of anti-NKR-P1 monoclonal antibody (mAb) 3.2.3, host NKs were depleted effectively in vivo after triple intraperitoneal injection prior to HSBTx. In contrast to non-depleted animals, an initial lack of NK activity in F1 hosts significantly decreased the mean survival (P < 0.01) and substantially enhanced graft-versus-host disease (GvHD)-related damage to lymphoid and non-lymphoid target organs. These findings emphasize the important immunoregulatory role of host NKs during the early onset of GvHD.

Animals↗