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Biomedical subjects

T Mohanakumar

Publications and source records attributed to T Mohanakumar.

At least 127 records · Page 7Linked to original sources
PubMed1998

The effect of tolerance to noninherited maternal HLA antigens on the survival of renal transplants from sibling donors.

BACKGROUND: During pregnancy and nursing, a baby's developing immune system is intimately exposed to the mother's antigens. To determine whether this exposure is of clinical benefit to patients who later receive an allograft as an adult, we analyzed the outcome of primary renal transplantations from sibling donors. METHODS: We retrospectively studied graft survival and rejection episodes in 205 patients who had received renal transplants at nine centers between 1966 and 1996 from sibling donors bearing maternal or paternal HLA antigens not inherited by the recipient. The sibling donors were categorized by analysis of family HLA-typing data. RESULTS: In the multicenter analysis, graft survival was higher at 5 years and at 10 years after transplantation in recipients of kidneys from siblings expressing maternal HLA antigens not inherited by the recipient than in recipients of kidneys from siblings expressing paternal HLA antigens not inherited by the recipient (86 percent vs. 67 percent at 5 years and 77 percent vs. 49 percent at 10 years, P=0.006 for both). Paradoxically, there was a higher incidence of early rejection in the former group, suggesting that fetal and neonatal exposure to maternal antigens results in immunologic priming. Pretransplantation transfusions of donor blood reduced the incidence of acute rejection while preserving the beneficial effect of tolerance to noninherited maternal antigens on graft survival. Since 1986, new immunosuppressive drugs have lessened the short-term, but not the long-term, survival advantage of grafts expressing maternal HLA antigens not inherited by the recipient. CONCLUSIONS: In the transplantation of a kidney from a sibling donor who is mismatched with the recipient for one HLA haplotype, graft survival is higher when the donor has maternal HLA antigens not inherited by the recipient than when the donor has paternal HLA antigens not inherited by the recipient.

Fathers↗
PubMed1998

HLA antibodies present in the sera of sensitized patients awaiting renal transplant are also reactive to swine leukocyte antigens.

BACKGROUND: To determine whether preformed HLA alloantibodies present in the sera of patients awaiting kidney transplantation will be detrimental to a potential porcine xenograft, we tested their cross-reactivity to swine leukocyte antigens (SLA). METHODS: Sera obtained from patients with varying levels of HLA sensitization (high panel-reactive antibodies > 70%, n= 7; moderate panel-reactive antibodies 30-40%, n=2) were analyzed. Pooled normal human AB sera and sera from nonsensitized patients (n=3) served as negative control. IgG was purified by protein-G chromatography, and xenoreactive natural antibodies (XNA) were depleted by passing the IgG through a series of melibiose and thyroglobulin-agarose columns. The elimination of XNA from HLA IgG preparations was confirmed by GS-IB4 lectin blocking assay and by an ELISA. RESULTS: IgG isolated from normal AB serum and three nonsensitized patients, which was depleted of XNA (HLA-IgG), did not react to human or porcine lymphocytes (peripheral blood mononuclear cells; PBMC) either by flow cytometry or by complement-dependent microcytotoxicity assays. However, HLA-IgG isolated from nine sensitized patients were reactive to a panel of porcine peripheral blood lymphocytes (n=6) by flow cytometry (>50 mean channel shift) and in complement-dependent microcytotoxicity assays in addition to their reactivity to human PBMC. The binding of HLA-IgG to porcine PBMC was significantly reduced by preabsorption with pooled human platelet concentrate. Further, the HLA IgG showed recognition of 45-kDa affinity-purified SLA class I on Western blots. CONCLUSIONS: This study demonstrates that HLA antibodies present in the sera of sensitized individuals can cross-react with SLA. Thus, xenotransplantation of porcine organs into HLA-sensitized patients has the potential to be rejected by humoral mechanisms. Testing to avoid such cross-reactive antibodies should be considered.

Animals↗
PubMed1998

T cell recognition of myelin proteolipid protein and myelin proteolipid protein peptides in the peripheral blood of multiple sclerosis and control subjects.

Myelin proteolipid protein (PLP) is a prime candidate autoantigen for multiple sclerosis. In order to define potential immunodominant epitopes, T cell lines (TCL) from the peripheral blood of HLA-DR 15(2) MS patients were established which responded to the intact molecule of PLP. These TCL were then tested in individual proliferation assays with a variety of PLP peptides spanning most of the PLP molecule. Multiple peptides were recognized by TCL from the MS population, with more than one peptide often recognized by lines from the same individual. Three immunodominant peptides were identified which were recognized by the majority of MS patients. Estimated frequency analyses were then performed on the peripheral blood of HLA-DR15(2)-positive MS and control subjects using TCL initiated by the three immunodominant peptides, 40-60, 95-117, and 185-206. TCL from HLA-DR15 MS subjects recognized peptide 95-117 significantly more often than TCL from control subjects.

Adult↗
PubMed1998

HLA-A locus mismatches and development of antibodies to HLA after lung transplantation correlate with the development of bronchiolitis obliterans syndrome.

BACKGROUND: Bronchiolitis obliterans syndrome (BOS) is the most common cause of morbidity and mortality after lung transplantation (LT). A retrospective analysis of clinical and immunologic variables were done to identify those that might predict the development of BOS. METHODS: Of 112 LT performed over a 42-month interval, 94 survived at least 3 months and form the basis of this analysis. There was a minimum of 21 months follow-up. BOS was defined on the basis of declining spirometry (FEV1 <80% of baseline) and/or the presence of histologic obliterative bronchiolitis. All variables analyzed were subjected first to a univariate analysis; those variables appearing to carry significance were then subjected to a multivariate logistic regression analysis. RESULTS: Univariate analysis revealed the following to be predictors of the development of BOS: age (the probability of developing BOS declined with advancing age); donor/recipient HLA-A locus mismatch, with actuarial freedom from BOS being significantly greater with no A-locus mismatches versus cases with one or two mismatches (P=0.031); and development of anti-HLA antibodies after transplantation (P=0.006 vs. recipients without detectable antibodies). In multivariate analysis, only HLA locus mismatch and development of anti-HLA antibodies were significant independent predictors of the development of BOS. The remaining clinical variables (gender, type of LT, indication for LT, graft ischemic time, use of cardiopulmonary bypass, cytomegalovirus) and immunologic variables (crossmatch, frequent early acute rejection) did not correlate with the development of BOS. CONCLUSIONS: These data suggest that BOS is the result of an immune process, that differences at the HLA-A locus may play an important role in this process, and antibody-mediated injury may play a role in BOS.

Adult↗
PubMed1998

Indirect recognition of porcine xenoantigens by human CD4+ T cell clones.

BACKGROUND: Human T-cell response against xenogeneic antigens may occur either by direct recognition of antigens on xenogeneic antigen-presenting cells (APCs) or by an indirect pathway mediated by autologous APCs. METHODS: The proliferative response of human CD4+ T cells to porcine aortic endothelial cells (PAECs) was measured. From these T-cell lines, eight CD4+ T-cell clones were obtained by limiting dilution. RESULTS: CD4+ T cells, in the absence of monocytes, proliferated in response to PAECs only after swine leukocyte antigen (SLA) class II molecules were induced on PAECs. The proliferation was significantly better when autologous human monocytes were added back as APCs. All of the eight CD4+ T-cell clones demonstrated specific proliferative response when stimulator PAECs, but not PAECs of other porcine origins, were preincubated with autologous human APCs before addition of these clones. These results indicated that the clones are recognizing porcine xenoantigens presented by self-APCs. The proliferative response of CD4+ T-cell clones was blocked by antibodies directed against human leukocyte antigen class II and human CD4, but not by anti-SLA class II monoclonal antibodies. A marked inhibition in proliferation was also noted when human APCs were incubated with chloroquine before addition to the cultures, indicating that xenoantigens had to be processed in order to be recognized by the clones. CONCLUSIONS: Human CD4+ T cells can recognize xenoantigens by either a direct or indirect pathway. The CD4+ T-cell clones developed against SLA class II-negative PAECs recognized strain-specific porcine xenoantigens indirectly.

Animals↗
PubMed1998

Effect of development of antibodies to HLA and cytomegalovirus mismatch on lung transplantation survival and development of bronchiolitis obliterans syndrome.

OBJECTIVE: A retrospective analysis was performed to examine the role of HLA antibodies and cytomegalovirus mismatch on the development of bronchiolitis obliterans syndrome and survival after lung transplantation. METHODS: Of 339 consecutive lung transplantations performed over a 102-month interval, 301 patients survived at least 3 months. There was a minimum follow-up period of 13 months. Bronchiolitis obliterans syndrome was defined as a decline in forced expiratory volume in 1 second less than 80% of posttransplantation baseline and/or histologic presence of obliterative bronchiolitis and was defined as occurring "early" if documented within 3 years of transplantation. Variables analyzed included preoperative donor and recipient cytomegalovirus status and the development of antibodies to human leukocyte antigens after transplantation. Microcytotoxicity was used to determine the presence of antibodies to human leukocyte antigens. Variables were subjected to Kaplan-Meier analysis to determine their impact on freedom from bronchiolitis obliterans syndrome and survival. RESULTS: The development of antibodies to human leukocyte antigens after transplantation correlated significantly with bronchiolitis obliterans syndrome (P = .02). The development of antibodies to human leukocyte antigens did not affect survival (P = .33) unless they were detected within 2 years of transplantation (P = .04). There was greater frequency of early bronchiolitis obliterans syndrome in cytomegalovirus seronegative patients who received allografts from seropositive donors compared with all other combinations (P = .02). There was also a trend toward worse survival of cytomegalovirus seronegative patients who received allografts from seropositive donors (P = .13). CONCLUSION: These data suggest that bronchiolitis obliterans syndrome is the result of an immune-mediated process in which HLA antibodies and cytomegalovirus may play a significant role.

Actuarial Analysis↗
PubMed1998

Characterization of HDJ-2, a human 40 kD heat shock protein.

Heat shock proteins (HSP) are a large and complex family of proteins that play important roles in cellular function and survival. In previous studies, cDNA for a 45 kD human HSP (HDJ-2) was cloned and shown to be homologous to DNA-J, a bacterial HSP [F.M. Ausubel, R. Brent, R. E. Kingston, D.D. Moore, J.G. Seidman, J.A. Smith, K. Struhl, Current Protocols in Molecular Biology, John Wiley and Sons, New York, 1997; A. Chellaiah, A. Davis, T. Mohanakumar, Cloning of a unique human homologue of the Escherichia coli DNAJ heat shock protein, Biochim. Biophys. Acta 1174 (1993) 111-113]. We have also shown that the expression of HDJ-2 is highly elevated in kidney allograft biopsies of kidneys undergoing rejection [Y.G. Alevy, D. Brennan, S. Durriya, T. Howard, T. Mohanakumar, Increased expression of the HDJ-2 heat shock protein in biopsies of human rejected kidneys, Transplantation 61 (1996) 963-967]. Because of the potential importance of HDJ-2 to disease pathogenesis, we carried out studies to characterize the structure and regulation of HDJ-2. Polyclonal and monoclonal antibodies that recognize recombinant HDJ-2 were prepared and used to localize its cellular expression. HDJ-2 was found to be farnesylated but not glycosylated. This HSP was ubiquitously expressed in all of the cell types we analyzed and was localized throughout the cytoplasm and around the nuclear membrane. However, upon heat shock it migrated to the Golgi, nucleolus, and the nuclear membrane. Northern blot analysis revealed two mRNA transcripts whose synthesis was not affected by heat shock. In addition, Western blot analysis showed that expression of HDJ-2 was also not affected by heat shock. Thus, our study shows the characterization of a HSP which, because of its migration pattern upon heat shock, is an excellent candidate for a protein chaperon.

Animals↗
PubMed1998

Analysis of graft-versus-host disease (GVHD) and graft rejection using MHC class I-deficient mice.

GVHD is a major complication in allogeneic bone marrow transplantation (BMT). MHC class I mismatching increases GVHD, but in MHC-matched BMT minor histocompatibility antigens (mH) presented by MHC class I result in significant GVHD. To examine the modification of GVHD in the absence of cell surface MHC class I molecules, beta2-microglobulin-deficient mice (beta2m(-/-)) were used as allogeneic BMT recipients in MHC- and mH-mismatched transplants. Beta2m(-/-) mice accepted MHC class I-expressing BM grafts and developed significant GVHD. MHC (H-2)-mismatched recipients developed acute lethal GVHD. In contrast, animals transplanted across mH barriers developed indolent chronic disease that was eventually fatal. Engrafted splenic T cells in all beta2m(-/-) recipients were predominantly CD3+alphabetaTCR+CD4+ cells (15-20% of all splenocytes). In contrast, CD8+ cells engrafted in very small numbers (1-5%) irrespective of the degree of MHC mismatching. T cells proliferated against recipient strain antigens and recognized recipient strain targets in cytolytic assays. Cytolysis was blocked by anti-MHC class II but not anti-CD8 or anti-MHC class I monoclonal antibodies (MoAbs). Cytolytic CD4+ T cells induced and maintained GVHD in mH-mismatched beta2m(-/-) mice, supporting endogenous mH presentation solely by MHC class II. Conversely, haematopoietic beta2m(-/-) cells were unable to engraft in normal MHC-matched recipients, presumably due to natural killer (NK)-mediated rejection of class I-negative cells. Donor-derived lymphokine-activated killer cells (LAK) were unable to overcome graft rejection (GR) and support engraftment.

Animals↗
PubMed1998

Increased expression of HDJ-2 (heat shock protein 40) and heat shock protein 70 in biopsy specimens of transplanted human lungs.

BACKGROUND: Heat shock proteins are expressed during several forms of stress and inflammation. This study was done to determine whether the expression of heat shock protein HDJ-2 (heat shock protein 40), heat shock protein 60, and heat shock protein 70 are increased during rejection in human pulmonary allografts. METHODS: Thirty-five transbronchial biopsy specimens were obtained from adult lung transplant recipients. Histologic analysis and assessment of heat shock protein HDJ-2, heat shock protein 60, and heat shock protein 70 mRNA expression was performed. Total RNA was extracted, reverse transcribed, and amplified by polymerase chain reaction with oligonucleotide primers specific for the heat shock proteins. The identity of the amplified message was verified by Southern blot and slot blot analysis. RESULTS: The expression of heat shock protein HDJ-2 was significantly higher in samples from lung transplant recipients undergoing rejection when compared with recipients without rejection or infection. Heat shock protein 70 expression was also increased in rejection. Expression of heat shock protein 60 did not show any increase in recipients with no evidence of rejection and infection or transplant recipients with rejection or infection. Serial analysis of heat shock protein HDJ-2 and heat shock protein 70 obtained in biopsy specimens during and after rejection showed a decrease of heat shock protein HDJ-2 and heat shock protein 70 expression after resolution of lung rejection. CONCLUSION: Our data demonstrate that the expression of heat shock protein HDJ-2 and heat shock protein 70 increases during lung rejection. However, only heat shock protein HDJ-2 was able to differentiate between rejection and infection. Measurement of heat shock protein HDJ-2 in transbronchial biopsy specimens may assist in the differential diagnosis between rejection and infection in lung transplant recipients.

Carrier Proteins↗
PubMed1997

Peripheral blood microchimerism in human liver and renal transplant recipients: rejection despite donor-specific chimerism.

BACKGROUND: Development of donor-specific microchimerism (DSM) has been proposed as one of the possible mechanisms for induction and maintenance of allograft tolerance. The aim of this study was to determine: (1) the state of DSM in liver transplant (LTx) and renal transplant (RTx) recipients, (2) whether the persistent presence of an allograft is a requirement for maintenance of chimerism, and (3) whether donor-specific blood transfusions (DST) facilitate chimerism development in RTx recipients and whether this correlates with allograft function. METHODS: Qualitative and quantitative analysis of DSM in peripheral blood of LTx and RTx recipients was assessed by polymerase chain reaction and competitive polymerase chain reaction using HLA-DR probes for mismatched antigens between the donor and recipient. RESULTS: LTx recipients (11 of 12) who had or were having rejection were positive for DSM in circulation compared with 4 of 11 with normal allograft function (P<0.01). The number of donor cells did not correlate with allograft function. LTx recipients (4 of 4) who lost their first allograft and underwent retransplantation retained DSM for the first donors. RTx recipients who received DST (8 of 8) were positive for DSM compared with 6 of 12 of nontransfused recipients (P<0.045). CONCLUSIONS: The results suggest that LTx and RTx recipients undergo rejection despite DSM. The development of DSM may not be a prerequisite for normal allograft function. Once DSM is established, the presence of the allograft is not required for maintenance of chimerism. DST facilitated the development of DSM in RTx recipients. Direct correlation was not observed between the development of DSM and allograft function in either DST or nontransfused RTx recipients.

Alleles↗
PubMed1997

Recognition of porcine major histocompatibility complex class I antigens by human CD8+ cytolytic T cell clones.

To evaluate the nature of the human cellular immune response to porcine xenoantigens, cytolytic T lymphocyte (CTL) cell lines were generated against porcine aortic endothelial cells (PAEC). After four stimulations, the phenotypes of the T cell lines were primarily CD8+ (79.7+/-19.6%). Natural killer cells were not detected. Functional analysis of the T cell lines showed specific cytotoxicity against syngeneic porcine targets with no lysis of unrelated porcine cells, human cells, or K562, a natural killer target. The major histocompatibility complex (MHC) specificity of this response was confirmed when T cell lines established against PAEC from partially inbred SLAdd miniature swine lysed only PAEC and phytohemagglutinin-stimulated lymphocytes from SLAdd origin but not SLAgg targets. Both CD8+ (7/12) and CD4+ (5/12) T cell clones were generated from the bulk cell lines. All of the CD8+ T cell clones specifically lysed stimulator PAEC and swine leukocyte antigen (SLA)-matched, phytohemagglutinin-stimulated lymphocyte targets but not unrelated porcine targets. CD4+ T cell clones, as expected, showed no lysis of any porcine target cells. The lysis of porcine targets by the human CD8+ cytotoxic T lymphocyte clones was inhibited by monoclonal antibodies against SLA class I antigens and human CD8, which indicates that human CD8+ T cells recognize porcine MHC class I molecules. These results, which show that human T cells differentiate between porcine MHC alleles, have relevance in the clinical application of xenografts.

Animals↗
PubMed1997

Human peripheral blood leukocyte-reconstituted severe combined immunodeficient mouse: analysis of the human immune response against porcine islet transplantation.

Human peripheral blood leukocyte (PBL)-reconstituted severe combined immunodeficient (SCID) mice (Hu-PBL-SCID) were used as a model to study xenograft rejection in humans. SCID mice were reconstituted with human PBL using a protocol that included a booster injection with anti-human CD3 antibody-primed cells. This protocol enhanced chimera establishment in SCID mice and resulted in the detection of higher levels of human Ig when compared with SCID mice receiving unprimed PBL alone. Human xenoreactive natural antibodies (XNA), both IgM and IgG subtypes, which recognized porcine islets (PI), were detected in sera of Hu-PBL-SCID by cytofluorometric analysis. Pretreatment of porcine cells with GS-IB4 lectin inhibited the XNA binding, demonstrating the specificity of the XNA from Hu-PBL-SCID. Western blot analysis showed that XNA from normal human serum and Hu-PBL-SCID serum recognized similar xenoantigens on PI, indicating that Hu-PBL-SCID contained a XNA repertoire representative of normal human serum. Immunofluorescent staining of the tissue sections revealed that both human IgG and IgM bound in vivo to the PI engrafted beneath the kidney capsule of Hu-PBL-SCID. In addition, mouse complement (C3) was detected on xenografted PI. The function of xenografted islets were monitored by measuring porcine insulin concentration using a radioimmunoassay. Porcine insulin concentration in the sera of both Hu-PBL-SCID and plain SCID xenografted with PI was similar for up to 14 days after transplantation, after which the insulin levels in Hu-PBL-SCID decreased, thereby indicating rejection. Therefore, PI transplanted into the Hu-PBL-SCID should be a useful model for the study of cellular as well as acquired humoral immune response against xenoislets.

Acute Disease↗
PubMed1997

Renal allograft infiltrating lymphocytes: frequency of tissue specific lymphocytes.

Acute rejection, mediated by T lymphocytes recognizing donor MHC class I and II, is a major factor influencing renal transplant survival. To define the specificity of these effector cells we examined cytolytic activity of graft infiltrating T lymphocytes (GIL) from renal biopsies of individuals undergoing acute cellular rejection. The majority of these cells recognized MHC class I on both donor kidney epithelial cells (KCL) and B-lymphoblastoid cells (LCL) suggesting these T cells recognized peptides from various tissues. However, cold target inhibition experiments demonstrated a significant proportion of GIL T cells were tissue specific. We reported previously that kidney specific CTL can be isolated from biopsies of kidney allografts undergoing acute cellular rejection. Here we extend that observation showing we were able to isolate tissue specific CTL from two additional biopsies. Greater than 10% of the clones isolated (4 of 36 and 5 of 37) from these biopsies were CTL recognizing donor KCL but not LCL targets suggesting that peptides, recognized in the context of donor MHC, were tissue specific. Repeated isolation of significant numbers of tissue specific CTL suggests these T cells play a role in allograft rejection and may be important effector cells mediating rejection in HLA matched transplants.

Adult↗
PubMed1997

Allograft infiltrating cytotoxic T lymphocytes recognize kidney-specific human minor histocompatibility antigens.

The role of minor histocompatibility antigens (mH) in allograft immunity has been proposed, but the nature of these antigens and their immunogenicity are not well understood. We have shown that tissue-specific cytolytic T lymphocytes (CTL) can be isolated form graft infiltrating lymphocyte (GIL) populations from renal transplant recipients undergoing acute cellular rejection. In most cases these CTL were allorestricted recognizing donor mismatched kidney MHC class I antigens. In contrast, one patient's GIL T cells demonstrated specific lytic activity against HLA-B35 expressed on primary kidney epithelial cell lines (KCL) but not on B-lymphoblastoid cell lines (LCL). Since HLA-B35 was a shared antigen between donor and recipient, these results suggest that CTL within the GIL population are recognizing a tissue-specific minor histocompatibility antigen presented in the context of self-HLA-B35.

Acute Disease↗