The Experts below are selected from a list of 123 Experts worldwide ranked by ideXlab platform
Rene J. Duquesnoy - One of the best experts on this subject based on the ideXlab platform.
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structural aspects of hla class i epitopes reacting with human monoclonal antibodies in ig binding c1q binding and Lymphocytotoxicity assays
Human Immunology, 2013Co-Authors: Rene J. Duquesnoy, Marilyn Marrari, Larry Jelenik, Adriana Zeevi, Frans H J Claas, Arend MulderAbstract:This study addresses the reactivity patterns of human cytotoxic HLA class I epitope-specific monoclonal antibodies in Ig-binding and complement component C1q-binding Luminex assays in comparison with complement-dependent Lymphocytotoxicity data reported at the 13th International HLA Workshop. Some monoclonal antibodies reacted similarly with epitope-carrying alleles in all three assays but others showed different reactivity patterns. These reactivity differences were analyzed with HLAMatchmaker and we incorporated the concept that eplets are essential parts of structural epitopes which can contact the six Complementarity Determining Regions (CDRs) of antibody. The data show that technique-dependent reactivity patterns are associated with distinct differences between polymorphic amino acid configurations on eplet-defined structural epitopes. The findings have been viewed in context of antigen-antibody complex formation that results in the release of free energy necessary to stabilize binding and to induce conformational changes in the antibody molecule to expose the C1q binding site, the first step of complement activation. Moreover the amount of free energy should be sufficient to induce a conformational change of C1q thereby initiating the first stages of the classical complement cascade leading to Lymphocytotoxicity. The complement-fixing properties of HLA antibodies require not only specific recognition of eplets but also depend on interactions of other CDRs with critical amino acid configurations within the structural epitope. Eplet-carrying alleles that lack such configurations may only bind with antibody. This concept is important to our understanding whether or not complement-fixing donor-specific HLA antibodies can initiate antibody-mediated rejection.
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multilaboratory evaluation of serum analysis for hla antibody and crossmatch reactivity by Lymphocytotoxicity methods
Archives of Pathology & Laboratory Medicine, 2003Co-Authors: Rene J. Duquesnoy, Marilyn MarrariAbstract:Abstract Context.—This report presents results of the serum antibody analysis and crossmatch challenges in the proficiency testing program for histocompatibility testing jointly sponsored by the American Society for Histocompatibility and Immunogenetics and the College of American Pathologists. Objective.—To obtain information about consensus rates among participating laboratories that reported antibody screening and crossmatch results by direct complement-dependent Lymphocytotoxicity (CDC) and/or anti-human globulin (AHG)–augmentation methods. Design.—We analyzed responses from approximately 165 laboratories participating in 32 surveys during 1993–2000. Most of the testing was done by CDC methods, but increasing proportions of laboratories are using AHG augmentation of these techniques; almost one half of the serum screenings and crossmatches were done by AHG. Results.—A total of 40 serum specimens were screened to determine the percent panel-reactive antibody (PRA) and identify HLA-specific antibodies. ...
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progress report on the ashi cap proficiency survey program in histocompatibility testing i hla a b c typing antibody screening and Lymphocytotoxicity crossmatching
Human Immunology, 1994Co-Authors: Marilyn Marrari, Rene J. DuquesnoyAbstract:The Histocompatibility Survey Program was organized in 1982 as a joint project by the ASHI and CAP to evaluate laboratory performance in HLA typing, Lymphocytotoxicity crossmatching, and antibody analysis. This report summarizes the experience with the HS surveys on HLA class I serology. During a 12-year period, the number of participating laboratories increased from 150 to 285 and HLA typing was done with 90 survey specimens representing 20 HLA-A and 35 HLA-B antigens. Most unsplit antigens were correctly identified in more than 90% of the laboratories. For many antigens, a high percentage of participants reported a split and there was generally a high consensus of a correct assignment. Nevertheless, several antigens were difficult to define, as shown by low consensus rates. During recent years, the assignments of Bw4/6 and HLA-C antigens have significantly improved. Lymphocytotoxicity crossmatching was analyzed for 138 cell-serum combinations tested by an average of 143 laboratories. Comparisons between four techniques (basic NIH, Amos modified, LI, and AHG) showed consistent results (greater than 90% crossmatch compatibility or incompatibility) for 71% of the cell-serum combinations. The crossmatch results with the remaining combinations were more variable for one or more of the crossmatch techniques. Serum antibody identification showed a continued improvement during recent years, and the average consensus for assigning acceptable antibody specificity reached 88%. A performance grading system based on a 90% consensus rate among participants is used to satisfy requirements for laboratory accreditation.
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Progress report on the ASHI/CAP proficiency survey program in histocompatibility testing I. HLA-A, B, C typing, antibody screening, and Lymphocytotoxicity crossmatching
Human immunology, 1994Co-Authors: Marilyn Marrari, Rene J. DuquesnoyAbstract:The Histocompatibility Survey Program was organized in 1982 as a joint project by the ASHI and CAP to evaluate laboratory performance in HLA typing, Lymphocytotoxicity crossmatching, and antibody analysis. This report summarizes the experience with the HS surveys on HLA class I serology. During a 12-year period, the number of participating laboratories increased from 150 to 285 and HLA typing was done with 90 survey specimens representing 20 HLA-A and 35 HLA-B antigens. Most unsplit antigens were correctly identified in more than 90% of the laboratories. For many antigens, a high percentage of participants reported a split and there was generally a high consensus of a correct assignment. Nevertheless, several antigens were difficult to define, as shown by low consensus rates. During recent years, the assignments of Bw4/6 and HLA-C antigens have significantly improved. Lymphocytotoxicity crossmatching was analyzed for 138 cell-serum combinations tested by an average of 143 laboratories. Comparisons between four techniques (basic NIH, Amos modified, LI, and AHG) showed consistent results (greater than 90% crossmatch compatibility or incompatibility) for 71% of the cell-serum combinations. The crossmatch results with the remaining combinations were more variable for one or more of the crossmatch techniques. Serum antibody identification showed a continued improvement during recent years, and the average consensus for assigning acceptable antibody specificity reached 88%. A performance grading system based on a 90% consensus rate among participants is used to satisfy requirements for laboratory accreditation.
Marilyn Marrari - One of the best experts on this subject based on the ideXlab platform.
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structural aspects of hla class i epitopes reacting with human monoclonal antibodies in ig binding c1q binding and Lymphocytotoxicity assays
Human Immunology, 2013Co-Authors: Rene J. Duquesnoy, Marilyn Marrari, Larry Jelenik, Adriana Zeevi, Frans H J Claas, Arend MulderAbstract:This study addresses the reactivity patterns of human cytotoxic HLA class I epitope-specific monoclonal antibodies in Ig-binding and complement component C1q-binding Luminex assays in comparison with complement-dependent Lymphocytotoxicity data reported at the 13th International HLA Workshop. Some monoclonal antibodies reacted similarly with epitope-carrying alleles in all three assays but others showed different reactivity patterns. These reactivity differences were analyzed with HLAMatchmaker and we incorporated the concept that eplets are essential parts of structural epitopes which can contact the six Complementarity Determining Regions (CDRs) of antibody. The data show that technique-dependent reactivity patterns are associated with distinct differences between polymorphic amino acid configurations on eplet-defined structural epitopes. The findings have been viewed in context of antigen-antibody complex formation that results in the release of free energy necessary to stabilize binding and to induce conformational changes in the antibody molecule to expose the C1q binding site, the first step of complement activation. Moreover the amount of free energy should be sufficient to induce a conformational change of C1q thereby initiating the first stages of the classical complement cascade leading to Lymphocytotoxicity. The complement-fixing properties of HLA antibodies require not only specific recognition of eplets but also depend on interactions of other CDRs with critical amino acid configurations within the structural epitope. Eplet-carrying alleles that lack such configurations may only bind with antibody. This concept is important to our understanding whether or not complement-fixing donor-specific HLA antibodies can initiate antibody-mediated rejection.
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multilaboratory evaluation of serum analysis for hla antibody and crossmatch reactivity by Lymphocytotoxicity methods
Archives of Pathology & Laboratory Medicine, 2003Co-Authors: Rene J. Duquesnoy, Marilyn MarrariAbstract:Abstract Context.—This report presents results of the serum antibody analysis and crossmatch challenges in the proficiency testing program for histocompatibility testing jointly sponsored by the American Society for Histocompatibility and Immunogenetics and the College of American Pathologists. Objective.—To obtain information about consensus rates among participating laboratories that reported antibody screening and crossmatch results by direct complement-dependent Lymphocytotoxicity (CDC) and/or anti-human globulin (AHG)–augmentation methods. Design.—We analyzed responses from approximately 165 laboratories participating in 32 surveys during 1993–2000. Most of the testing was done by CDC methods, but increasing proportions of laboratories are using AHG augmentation of these techniques; almost one half of the serum screenings and crossmatches were done by AHG. Results.—A total of 40 serum specimens were screened to determine the percent panel-reactive antibody (PRA) and identify HLA-specific antibodies. ...
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progress report on the ashi cap proficiency survey program in histocompatibility testing i hla a b c typing antibody screening and Lymphocytotoxicity crossmatching
Human Immunology, 1994Co-Authors: Marilyn Marrari, Rene J. DuquesnoyAbstract:The Histocompatibility Survey Program was organized in 1982 as a joint project by the ASHI and CAP to evaluate laboratory performance in HLA typing, Lymphocytotoxicity crossmatching, and antibody analysis. This report summarizes the experience with the HS surveys on HLA class I serology. During a 12-year period, the number of participating laboratories increased from 150 to 285 and HLA typing was done with 90 survey specimens representing 20 HLA-A and 35 HLA-B antigens. Most unsplit antigens were correctly identified in more than 90% of the laboratories. For many antigens, a high percentage of participants reported a split and there was generally a high consensus of a correct assignment. Nevertheless, several antigens were difficult to define, as shown by low consensus rates. During recent years, the assignments of Bw4/6 and HLA-C antigens have significantly improved. Lymphocytotoxicity crossmatching was analyzed for 138 cell-serum combinations tested by an average of 143 laboratories. Comparisons between four techniques (basic NIH, Amos modified, LI, and AHG) showed consistent results (greater than 90% crossmatch compatibility or incompatibility) for 71% of the cell-serum combinations. The crossmatch results with the remaining combinations were more variable for one or more of the crossmatch techniques. Serum antibody identification showed a continued improvement during recent years, and the average consensus for assigning acceptable antibody specificity reached 88%. A performance grading system based on a 90% consensus rate among participants is used to satisfy requirements for laboratory accreditation.
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Progress report on the ASHI/CAP proficiency survey program in histocompatibility testing I. HLA-A, B, C typing, antibody screening, and Lymphocytotoxicity crossmatching
Human immunology, 1994Co-Authors: Marilyn Marrari, Rene J. DuquesnoyAbstract:The Histocompatibility Survey Program was organized in 1982 as a joint project by the ASHI and CAP to evaluate laboratory performance in HLA typing, Lymphocytotoxicity crossmatching, and antibody analysis. This report summarizes the experience with the HS surveys on HLA class I serology. During a 12-year period, the number of participating laboratories increased from 150 to 285 and HLA typing was done with 90 survey specimens representing 20 HLA-A and 35 HLA-B antigens. Most unsplit antigens were correctly identified in more than 90% of the laboratories. For many antigens, a high percentage of participants reported a split and there was generally a high consensus of a correct assignment. Nevertheless, several antigens were difficult to define, as shown by low consensus rates. During recent years, the assignments of Bw4/6 and HLA-C antigens have significantly improved. Lymphocytotoxicity crossmatching was analyzed for 138 cell-serum combinations tested by an average of 143 laboratories. Comparisons between four techniques (basic NIH, Amos modified, LI, and AHG) showed consistent results (greater than 90% crossmatch compatibility or incompatibility) for 71% of the cell-serum combinations. The crossmatch results with the remaining combinations were more variable for one or more of the crossmatch techniques. Serum antibody identification showed a continued improvement during recent years, and the average consensus for assigning acceptable antibody specificity reached 88%. A performance grading system based on a 90% consensus rate among participants is used to satisfy requirements for laboratory accreditation.
G.a. Teresi - One of the best experts on this subject based on the ideXlab platform.
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Variations of the Lymphocytotoxicity test. An evaluation of sensitivity and specificity.
Transplantation, 1995Co-Authors: Andrea A. Zachary, Lynne Klingman, Nancy Thorne, Alan R. Smerglia, G.a. TeresiAbstract:Multiple variations of the basic Lymphocytotoxicity test have been reported to increase test sensitivity. Although these modifications are used routinely in crossmatch tests, as required by federal regulation, there has been no methodical assessment of the relative sensitivities and specificities of these techniques, with the exception of the well-studied antiglobulin method. We have performed such a comparison and found that these modifications do not, uniformly, increase test sensitivity. We also observed that the effect of a technique modification on test sensitivity as measured by overall lymphocytotoxic antibody titer does not reflect, necessarily, the effect on HLA-specific antibody. It is widely believed that the antiglobulin method is the most sensitive of the Lymphocytotoxicity techniques. We observed that while the antiglobulin method increased overall test sensitivity dramatically, we achieved a comparable level of sensitivity by either substituting B cells for T cells or doubling both the serum and the complement incubation times. However, no other technique modification detected as many HLA antibody specificities as did the antiglobulin method. The data presented here provide useful guidelines for selecting techniques for HLA typing, antibody screening, and cross-matching.
Andrea A. Zachary - One of the best experts on this subject based on the ideXlab platform.
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Variations of the Lymphocytotoxicity test. An evaluation of sensitivity and specificity.
Transplantation, 1995Co-Authors: Andrea A. Zachary, Lynne Klingman, Nancy Thorne, Alan R. Smerglia, G.a. TeresiAbstract:Multiple variations of the basic Lymphocytotoxicity test have been reported to increase test sensitivity. Although these modifications are used routinely in crossmatch tests, as required by federal regulation, there has been no methodical assessment of the relative sensitivities and specificities of these techniques, with the exception of the well-studied antiglobulin method. We have performed such a comparison and found that these modifications do not, uniformly, increase test sensitivity. We also observed that the effect of a technique modification on test sensitivity as measured by overall lymphocytotoxic antibody titer does not reflect, necessarily, the effect on HLA-specific antibody. It is widely believed that the antiglobulin method is the most sensitive of the Lymphocytotoxicity techniques. We observed that while the antiglobulin method increased overall test sensitivity dramatically, we achieved a comparable level of sensitivity by either substituting B cells for T cells or doubling both the serum and the complement incubation times. However, no other technique modification detected as many HLA antibody specificities as did the antiglobulin method. The data presented here provide useful guidelines for selecting techniques for HLA typing, antibody screening, and cross-matching.
Lynne Klingman - One of the best experts on this subject based on the ideXlab platform.
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Variations of the Lymphocytotoxicity test. An evaluation of sensitivity and specificity.
Transplantation, 1995Co-Authors: Andrea A. Zachary, Lynne Klingman, Nancy Thorne, Alan R. Smerglia, G.a. TeresiAbstract:Multiple variations of the basic Lymphocytotoxicity test have been reported to increase test sensitivity. Although these modifications are used routinely in crossmatch tests, as required by federal regulation, there has been no methodical assessment of the relative sensitivities and specificities of these techniques, with the exception of the well-studied antiglobulin method. We have performed such a comparison and found that these modifications do not, uniformly, increase test sensitivity. We also observed that the effect of a technique modification on test sensitivity as measured by overall lymphocytotoxic antibody titer does not reflect, necessarily, the effect on HLA-specific antibody. It is widely believed that the antiglobulin method is the most sensitive of the Lymphocytotoxicity techniques. We observed that while the antiglobulin method increased overall test sensitivity dramatically, we achieved a comparable level of sensitivity by either substituting B cells for T cells or doubling both the serum and the complement incubation times. However, no other technique modification detected as many HLA antibody specificities as did the antiglobulin method. The data presented here provide useful guidelines for selecting techniques for HLA typing, antibody screening, and cross-matching.
