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T Mohanakumar

Publications and source records attributed to T Mohanakumar.

At least 73 records · Page 4Linked to original sources
PubMed2001

Prevention of obliterative airway disease in HLA-A2-transgenic tracheal allografts by neutralization of tumor necrosis factor.

BACKGROUND: Inflammatory cytokines play an important role in the development of experimental obliterative airway disease (OAD) after transplantation. To further determine the immunologic mechanisms associated with OAD development, we used a murine tracheal transplant model in which a single mismatched HLA-A2-transgenic molecule is indirectly recognized by the recipient CD4+ T cells and then determined whether neutralization of several inflammatory cytokines affected the development of OAD. METHODS: Tracheas from HLA-A2+ C57BL/6 mice were heterotopically transplanted into C57BL/6 mice. Recipients were treated with neutralizing antibodies against tumor necrosis factor (TNF), interferon-gamma (IFN-gamma), or interleukin-1 (IL-1). Allograft histology as well as anti-HLA-A2 antibody development and T cell proliferative responses were determined at days +5, +15, +28, and +60. RESULTS: Allografts in untreated and anti-IFN-gamma-treated recipients demonstrated full development of OAD by day +28. Allografts in anti-TNF-treated recipients showed no evidence of OAD, even at day +60. Allografts in anti-IL-1-treated recipients showed airway epithelium changes by day +28 but minimal evidence of OAD by day +60. Spleen cells from untreated and anti-IFN-gamma-treated recipients showed significantly higher proliferative responses to HLA-A2+ cells, compared with syngeneic recipients (negative controls). In contrast, anti-TNF and anti-IL-1-treated recipients showed significantly lower proliferative responses to HLA-A2+ cells, compared with untreated recipients. Development of anti-HLA-A2 antibodies was detected in all recipients by day +15, with the exception of those treated with anti-TNF. CONCLUSION: Among the inflammatory cytokines, TNF seems to play a crucial role in the immunopathology of OAD developed after transplantation.

Airway Obstruction↗
PubMed2001

Activation of human dendritic cells by porcine aortic endothelial cells: transactivation of naïve T cells through costimulation and cytokine generation.

BACKGROUND: Dendritic cells (DC) are the most potent antigen-presenting cells in the immune system. To define the role of human DC in human anti-porcine immune responses, we defined the interaction of human DC with porcine aortic endothelial cells (PAEC). METHODS: To determine the immune responses, both monocyte-derived and peripheral blood DC were cultured with porcine and human endothelial cells. We analyzed the role of CD11a, CD11b, and CD54 in a cell-to-cell adhesion assay using antibodies against these molecules. The expression pattern of costimulatory molecules (CD40, CD80, CD86), adhesion molecules (CD54), and intracellular cytokines (interleukin-12p70 and tumor necrosis factor [TNF]-alpha) in DC after interaction with endothelial cells was determined by immunofluorescence. RESULTS: Human DC significantly adhered to PAEC (38-40%), and this adhesion was augmented (>50%) upon treatment with either recombinant swine interferon-gamma or recombinant human TNF-alpha. Addition of human DC to PAEC was blocked by pretreatment of DC with antibodies specific to human leukocyte function-associated antigen-1 or CD54. Adhesion of DC to PAEC also resulted in the activation of DC, which was manifested by up-regulation of costimulatory molecules (CD40, CD80, CD86), adhesion molecules (CD54), and HLA-DR. PAEC-activated human DC provided proliferative signals to the naïve autologous CD4+ T cells and synthesized interleukin-12p70 and TNF-alpha. However, activated DCs failed to lyse PAEC in such interaction. CONCLUSION: Human DC effectively adhered to PAEC and were activated by xenoantigen, resulting in highly efficient antigen presentation and proliferation of CD4+ T cells. Further, this interaction of human DC to PAEC is regulated by the participation of costimulatory and adherence molecules and cytokines.

Animals↗
PubMed2001

Tissue-specific peptides influence human T cell repertoire to porcine xenoantigens.

BACKGROUND: Human CD8+ T cells elicit a vigorous response to allo- or xenogeneic MHC class I molecules. However, the influence of a given MHC-bound peptide to the responding allo- or xenoreactive T cell repertoire is not clear. METHODS: In this study, we analyzed individual T cell responses to unique tissue epitopes presented on syngeneic porcine endothelial and lymphoblastoid cells by limiting dilution analysis and analyzed the responding T cell repertoire by T cell receptor beta (TCR Vbeta) chain spectrotyping. RESULTS: Both porcine endothelial and lymphoblastoid cells were able to elicit swine leukocyte antigen (SLA) class I restricted and peptide-dependent cytotoxic T lymphocyte (CTL) responses. The responding human CD8+ T cells showed a heterogenous but limited TCR Vbeta gene usage. Interestingly, although a large portion of the selected TCR Vbeta gene usage in response to endothelial and lymphoblastoid cells were shared (i.e., Vbeta-1, 2, 6.1, 13), unique Vbeta usage was noted in T cells that respond to either endothelial (Vbeta-5.3) or lymphoblastoid cells (Vbeta-5.1, 11), suggesting that porcine tissue-specific epitopes play a role in modulating the responding T cell repertoire. Limiting dilution cloning analysis revealed that a majority (89%) of the CTL clones stimulated by porcine endothelial cells recognized shared peptides presented by both endothelial cells and syngeneic lymphoblastoid cells. However, a significant portion (11%) of the CTL clones recognized unique peptides presented only in the context of SLA class I molecules on endothelial cells. CONCLUSION: These results provide evidence for the first time that tissue-specific peptides can directly influence T cell repertoire in response to the xenogeneic stimulus.

Animals↗
PubMed2001

CD4+ T cell recognition of a single discordant HLA-A2-transgenic molecule through the indirect antigen presentation pathway induces acute rejection of murine cardiac allografts.

To further define the role of indirect allorecognition, cardiac allografts from HLA-A2-transgenic (HLA-A2+) C57BL/6 mice were heterotopically transplanted into normal C57BL/6, CD4 T cell-knockout (KO) C57BL/6 mice, CD8 T cell-KO C57BL/6 mice, fully MHC-discordant BALB/c mice (allogeneic control), and HLA-A2+ C57BL/6 mice (syngeneic control). HLA-A2+ grafts were acutely rejected when transplanted into BALB/c mice (mean survival time: 10+/-0.8 days), normal C57BL/6 mice (mean survival time: 16.5+/-2.1 days) as well as CD8-KO mice (mean survival time: 12.8+/-1.3 days). Histopathological analysis revealed classical acute cellular rejection with moderate to severe diffuse interstitial CD4+ and CD8+ cellular infiltrates and significant intra-graft deposition of IgG and complement. In contrast, HLA-A2+ grafts were not rejected when transplanted into CD4-KO mice or HLA-A2+ mice. CD8-KO recipients treated with an anti-CD4 monoclonal antibody, but not with an anti-NK monoclonal antibody, failed to reject their allografts with prolonged administration of antibody (30 days). Spleen cells from mice rejecting HLA-A2+ allografts failed to lyse HLA-A2+ target cells indicating a lack of involvement of CD8+ T cells in the rejection process. In contrast, spleen cells from rejecting animals proliferated significantly to both HLA-A2+ cells and to a peptide derived from the HLA-A2 molecule. Development of anti-HLA-A2 antibodies was observed in all animals rejecting HLA-A2+ allografts. These results suggest that indirect allorecognition of donor MHC class I molecules leads to rejection of cardiac allografts and development of alloantibodies in this unique transplant model in which there is a single MHC discordance between donor and recipient.

Acute Disease↗
PubMed2001

Activation of human airway epithelial cells by non-HLA antibodies developed after lung transplantation: a potential etiological factor for bronchiolitis obliterans syndrome.

BACKGROUND: The main cause of morbidity and mortality after lung transplantation (LT) is bronchiolitis obliterans syndrome (BOS). Anti-HLA antibodies development after LT has been shown to play an important role in BOS pathogenesis. However, the nature of non-HLA antibodies developed after LT and their role in BOS pathogenesis have not been determined. METHODS: Sera from 16 BOS+ patients and 11 BOS- patients were collected at 12, 24, 36, and 48 months after LT. Anti-HLA class I and class II antibodies were absorbed with pooled human platelets and pooled human lymphoblastoid cell lines, respectively. Then, the presence of non-HLA antibodies against several cell lines from different origin was determined by flow cytometric analysis. Antibody-positive samples were tested for induction of proliferation and growth factor production in two selected airway epithelial cell (AEC) lines. RESULTS: Five of 16 BOS+ patients (31.2%) and 0 of 11 BOS- patients (0%) developed anti-AEC antibodies after LT (P=0.05). No reactivity against endothelial cells, lymphocytes, monocytes, or granulocytes was detected. Further analysis of two selected sera demonstrated the development of reactivity against a 60-kDa antigen expressed by 60% of AEC lines and only 12% of cell lines from other tissues. Antibody binding to this antigen induced intracellular Ca++ influx, tyrosine phosphorylation, proliferation, and up-regulation of transforming growth factor-beta and heparin-binding epidermal growth factor mRNA transcription in AECs. CONCLUSIONS: These results indicate that anti-AEC antibodies may play a role in the immunopathogenesis of BOS in the absence of anti-HLA antibodies.

Antibodies↗
PubMed2001

A subcutaneous heterotopic limb transplantation model in the mouse for prolonged allograft survival.

A heterotopic position of a limb allograft is advantageous in the fragile mouse model to reduce mortality but is prone to autotomy. The purpose of this study was to describe a new heterotopic limb transplantation model in the mouse for prolonged allograft survival. Eleven lower hindlimbs were transplanted in a heterotopic subcutaneous position in the groin of the recipient animal with the donor skin inset as a skin paddle for monitoring. Seven transplants were syngeneic (Balb/c) and four were allogeneic (C57Bl/6 donor). The overall success rate (acute survival < 7 days) was 73% (8/11) and the mortality rate was 18% (2/11). Five of seven syngeneic transplants survived for 60 days and were harvested for histology. Recipients of successful allogeneic transplants (n = 3) received no immunosuppression and rejected their allografts between 8 and 11 days postoperatively. Mixed lymphocyte culture and flow cytometry demonstrated secondary immune responses by pre-sensitized animals, and histology showed lymphocytic infiltration and necrosis consistent with acute rejection.

Animals↗
PubMed2001

Defective apoptosis in lymphocytes and the role of IL-2 in autoimmune hematologic cytopenias.

Fas-mediated signaling is important for lymphocyte elimination. We investigated lymphocytes for Fas-signaling defects in 20 pediatric patients with chronic hematologic autoimmunity. In 5 of 20 (25%), there was profound resistance to exogenous FasL-mediated lysis, Fas mAb, and anti-CD3. FasL function, though variable, was not significantly different from that of simultaneously evaluated controls. Only 1 patient had a Fas mutation and manifestations of autoimmune lymphoproliferative syndrome. In contrast, lymphocytes from his clinically normal mother with the same mutation were normally sensitive to FasL. In 3 patients, normal Fas-mediated lysis was restored with rhIL-2. IL-2 had no effect in the other 2 patients. Activation and proliferation functions of IL-2 were normal in all 5. We conclude that altered Fas signaling, independent of Fas mutations, can precipitate hematologic autoimmunity. IL-2 can rescue some lymphocytes from this defect. In IL-2 refractory cases, a persistently defective response to IL-2 continues to confer a lymphocyte survival advantage. Hence, altered Fas pathway signaling with or without defective IL-2 responses should be considered in the etiology of hematologic autoimmunity.

Adolescent↗
PubMed2001

The association of HLA class II with pars planitis.

PURPOSE: To investigate the association of HLA class II alleles with pars planitis. METHODS: Blood samples were obtained from 28 patients with pars planitis seen in the Department of Ophthalmology and Visual Sciences and the Barnes Retina Institute at Washington University, St. Louis, Missouri. RESULTS: HLA-DR15, one of the allelic subtypes of HLA-DR2, was present in 18 (64.3%) of 28 patients vs. 10 (20%) of 50 controls (OR = 7.20, CI = 2.28--23.20, P =.0001). HLA-DR51 (HLA-DRB 5) was present in 16 (57.1%) of 28 patients vs. 6 (12%) of 50 controls (OR = 9.78, CI = 2.79--36.42, P =.0001). HLA-DR17 was present in eight (28.6%) of 28 patients vs. one (2%) of 50 controls (OR = 19.60, CI = 2.29--886.7, P =.0001). CONCLUSION: Pars planitis is associated with an increased frequency of the HLA-DR2 suballele, -DR15, HLA-DR51, and HLA-DR17. These results suggest an immunogenic predisposition exists to pars planitis.

Adolescent↗
PubMed2001

Recipient intramuscular gene transfer of active transforming growth factor-beta1 attenuates acute lung rejection.

BACKGROUND: Gene transfer into the donor graft has been demonstrated to be feasible in reducing ischemia-reperfusion injury and rejection in lung transplantation. This study was undertaken to determine whether intramuscular gene transfer into the recipient can also reduce subsequent lung graft rejection. METHODS: Brown Norway rats served as donors and F344 rats as recipients. Recipient animals were injected with 10(10) plaque-forming units of adenovirus encoding active transforming growth factor beta1 (group I, n = 6), beta-galactosidase as adenoviral controls (group II, n = 6), or normal saline without adenovirus (group III, n = 6) into both gluteus muscles 2 days before transplantation. Gene expression was confirmed by enzyme-linked immunosorbent assay. Graft function was assessed on postoperative day 5. RESULTS: Successful gene transfection and expression were confirmed by the presence of active transforming growth factor beta1 protein in muscle and plasma. Oxygenation was significantly improved in group I (group I vs II and III, 353.6 +/- 63.0 mm Hg vs 165.7 +/- 39.9 and 119.1 +/- 41.5 mm Hg; p = 0.02 and 0.004). The muscle transfected with the transforming growth factor beta1 showed granulation tissue with fibroblast accumulation. CONCLUSIONS: Intramuscular adenovirus-mediated gene transfer of active transforming growth factor beta1 into the recipients attenuates acute lung rejection as manifested by significantly improved oxygenation in transplanted lung allografts. This intramuscular transfection approach as a cytokine therapy is feasible in transplantation and may be useful in reducing rejection as well as reperfusion injury.

Adenoviridae↗
PubMed2001

Improved methods for the isolation and purification of porcine islets.

Recent progress in human islet transplantation demonstrates the feasibility of using purified human islets for treatment of type 1 diabetes mellitus; however, a shortage of human pancreata remains a major obstacle. This report describes methods to isolate porcine islets using a modification of the automated chamber method. The pancreata from 2-year-old sows were trimmed and injected intraductally with Sevac, Sigma, or Liberase PI collagenase. The pancreata was placed in the chamber, shaken, and recirculated at 70 ml/min until an adequate number of islets were liberated. The digest was centrifuged and the pellets pooled with University of Wisconsin Solution + 10% horse serum and incubated at 4 degrees C for 1 h. The islets were purified using a continuous gradient of Hypaque Euroficoll on a refrigerated COBE 2991. The islets were collected in fractions, assessed for purity, sized, and then suspended in Medium 199. Collagenase preparations obtained from Sevac (2919 islet equivalents [IE]/g), Sigma (2543 IE/g), and Liberase PI (2901 IE/g) gave similar results with 94%-95% purity. In summary, we report a successful method for efficient isolation and purification of porcine islets, yielding nearly 3000 IE/gm, with different collagenase products.

Animals↗
PubMed2001

Indirect allorecognition of mismatched donor HLA class II peptides in lung transplant recipients with bronchiolitis obliterans syndrome.

A correlation between indirect allorecognition of mismatched donor HLA class I peptides and development of bronchiolitis obliterans syndrome (BOS) after lung transplantation has been previously observed. The aim of this study was to determine whether there was a correlation between indirect allorecognition of mismatched donor HLA class II peptides and development of BOS after lung transplantation. Peripheral blood mononuclear cells from nine BOS+ and nine BOS-lung transplant recipients were cultured with synthetic peptides corresponding to the beta-chain hypervariable region of a mismatched donor HLA-DR molecule. Then, proliferative alloreactivity as well as frequency of alloreactive T cells were determined. In addition, the immunodominant epitopes from the donor HLA-DR molecules were identified in selected patients. T cells from BOS+ patients showed a dose-dependent proliferative alloreactivity against donor HLA-DR peptides that was significantly higher than that observed in BOS- patients (p=0.001). Similarly, the frequency of HLA-DR alloreactive T cells was significantly higher in BOS+ patients than in BOS- patients (p=0.001). This T-cell alloreactivity was directed against a single immunodominant HLA-DR peptide. These results suggest that indirect alloreactivity to donor HLA class II molecules may play a role in the pathogenesis of BOS after lung transplantation.

Amino Acid Sequence↗
PubMed2001

Development of a mouse model for heterotopic limb and composite-tissue transplantation.

The mouse remains the most suitable model to study the complexities of the immune system and transplant rejection. The purpose of this study was to describe a new mouse model for heterotopic limb and composite tissue transplantation. Eighteen procedures were performed, including 10 heterotopic lower hind limb, four vascularized skin, and four vascularized muscle transplantations. Three transplants were allogeneic, and the rest were syngeneic. All successful syngeneic transplants were harvested at 11 days postoperatively, except for one skin and one limb transplant that were followed for over 30 days. The allogeneic transplants showed signs of rejection between 7 to 11 days postoperatively. Results of mixed lymphocyte culture (p < 0.05) and histology evaluations from the allogeneic recipients were consistent with acute rejection as the cause of allograft loss. The mortality rate was 16.7 percent, and the overall success rate was 72.2 percent. Details of the operative procedure are described, and important technical factors are discussed.

Animals↗
PubMed2001

Renal transplantation following previous heart, liver, and lung transplantation: an 8-year single-center experience.

BACKGROUND: Long-term follow-up of heart, liver, and lung transplantation has led to an increased recognition of secondary end-stage renal failure (ESRF) in transplant recipients. This study examines our center's experience with renal transplantation following previous solid organ transplantation. METHODS: From January 1, 1992, to September 30, 1999, our center performed 18 renal transplants in previous solid organ recipients. During the same period, 815 total renal transplants were performed. One- and 3-year graft and patient survival, recipient demographics, donor type, and reason for transplantation were compared between these groups. RESULTS: Of the 18 recipients, 7 had prior heart transplants, 4 had prior liver transplants, and 7 had prior lung transplants. Cyclosporine toxicity contributed to renal failure in 17 (94.4%) of the patients-either as a sole factor (11 patients) or in combination with hypertension, renal artery stenosis, or tacrolimus toxicity (6 patients). Kaplan-Meier 1- and 3-year patient survival was 82.9% and 73.7%, compared with 95.5% and 90.7% in all renal transplant recipients. No surviving patient has suffered renal allograft loss. Mean current creatinine level is 1.4 mg/dL. CONCLUSIONS: Renal transplantation is an excellent therapy for ESRF following prior solid organ transplantation. One and 3-year patient and graft survival demonstrate the utility of renal transplantation in this patient population.

Follow-Up Studies↗
PubMed2001

Lipid-mediated ex vivo gene transfer of viral interleukin 10 in rat lung allotransplantation.

BACKGROUND: Recent studies suggest that viral interleukin 10 suppresses alloimmune response in transplantation and that cationic lipids are one of the most promising nonviral vehicles for gene therapy. The aim of this study was to examine the effect of ex vivo lipid-mediated viral IL10 gene transfer into rat lung allografts on subsequent rejection. METHODS: Male F344 rats (RT1lvl) underwent left lung transplantation with allografts from Brown Norway rats (RT1n). Allografts were transvascularly transfected 15 minutes after harvest with 5 mL of 1:20-diluted (group 1, n = 7) or 1:40-diluted (group 2, n = 6) GL67-pCMVievIL-10 complex. Group 3 (n = 7), serving as the control group, received 1:40-diluted GL67-pCF1-chloramphenicol acetyltransferase complex. All allografts were preserved for 3 hours at 10 degrees C before transplantation. In all groups recipients were killed on postoperative day 5. Transgene expression of viral interleukin 10 was assessed by means of both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Histologic rejection score, allograft gas exchange, exhaled nitric oxide level, and allograft cytokine mRNA expression were also assessed. RESULTS: Dose-dependent transgene expression of viral interleukin 10 was detected by means of both reverse transcriptase-polymerase chain reaction and immunohistochemistry. Allograft gas exchange (PaO2) in groups 1 (114.06 +/- 61.1 mm Hg) and 2 (108.58 +/- 35.7 mm Hg) was significantly better than that in group 3 (66.4 +/- 8.22 mm Hg; P =.020 and P =.023, respectively). The vascular rejection score in group 1 was significantly lower than that in group 3 (P =.032, Kruskal-Wallis test). Exhaled nitric oxide levels in group 2 (5.150 +/- 6.38 ppb) were significantly lower than those in group 3 (13.517 +/- 10.4 ppb; P =.039). Allograft interleukin 2 mRNA expression levels in group 1 (1.123 +/- 0.23 relative units) were significantly lower than those in group 3 (1.753 +/- 0.71 relative units; P =.038 vs group 3). CONCLUSIONS: Lipid-mediated ex vivo viral IL10 gene transfer into rat lung allografts improved graft gas exchange, reduced histologic rejection scores, downregulated graft interleukin 2 mRNA expression, and reduced exhaled nitric oxide levels by postoperative day 5. These results suggest a therapeutic potential of graft viral IL10 gene transfer as an effective immunosuppressive strategy against lung allograft rejection.

Animals↗