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First Movement Practicale: Fine-tuning the Instrument of Epitope-Based Histocompatibility Rene Duquesnoy University of Pittsburgh Medical Center.

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Presentation on theme: "First Movement Practicale: Fine-tuning the Instrument of Epitope-Based Histocompatibility Rene Duquesnoy University of Pittsburgh Medical Center."— Presentation transcript:

1 First Movement Practicale: Fine-tuning the Instrument of Epitope-Based Histocompatibility Rene Duquesnoy University of Pittsburgh Medical Center

2 Lecture Outline Immunogenicity and antigenicity of epitopes CDRs and antigen-antibody interactions HLAMatchmaker analysis of antibody reactivity with Luminex single allele panels Commonly recognized class II epitopes Epitope immunogenicity HLAMatchmaker and platelet transfusions

3 Identification of Structurally Defined HLA Epitopes Empirical approach –Look for correlations between antibody reactivity patterns and the presence of distinct polymorphic amino acid residues in different sequence positions on reactive alleles –Conduct absorption/elution of sera with selected alleles HLAMatchmaker –Epitope structure is based on three-dimensional modeling of different antigen- antibody complexes, molecular contact points between epitope and paratope and the contribution of important residues to epitope functionality –Consider the immunogenetic relationship between antibody producer and immunizer: concept of immunogenicity versus antigenicity –Determine if the antibody reactivity patterns correspond to HLAMatchmaker- predicted epitope mismatches

4 Differentiate between Immunogenicity of epitopes (induction of specific antibodies) and Antigenicity of epitopes (reactivity with antibodies) Important Consideration

5 HLA Mismatch Immunogenicity Mismatched HLA antigens have different epitope loads HLA epitopes have different degrees of immunogenicity A better understanding of HLA immunogenicity will permit a permissible mismatch strategy for non-sensitized transplant patients

6 Antigenicity Reactivity of epitopes with specific antibodies Serum screening methods –Complement-dependent lymphocytotoxicity: CDC, AHG –Antigen-binding assays: Elisa, Flow cytometry, Luminex with single antigens Technique-dependent antibody reactivity

7 How Do Antibodies React with Antigens?

8 Six Complementarity-Determining Regions of the Antibody Combining Site CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2 and CDR-L3 represent the “binding face” or “paratope” which contacts the structural epitope comprising amino acids

9 Crystal Structure of HLA-A1-MAGE-A1 Complex with Fab-Hyb3 Hulsmeyer et al. J. Biol. Chem., : , 2005

10 T-Cell Receptor-HLA Complex TCR HLA  

11 Six Complementarity-Determining Regions of the Antibody Combining Site CDR-H1, CDR-H2, CDR-H3, CDR-L1, CDR-L2 and CDR-L3 represent the “binding face” or “paratope” which contacts the structural epitope comprising amino acids The antibody specificity is often determined by a centrally located loop (CDR-H3) that binds to the functional epitope a configuration of 3-6 amino acids in the structural epitope Eplets may define these functional epitopes Other CDRs serve as contact sites to stabilize binding to antigen (they play a role in the affinity of antibody)

12 Noncovalent Forces in Antigen-Antibody Complexing Electrostatic forces Attraction between opposite charges Hydrogen bondsHydrogen shared between electronegative atoms (N,O) Van der Waals forces Fluctuations in electron clouds around molecules oppositely polarize neighboring atoms Hydrophobic forces Hydrophobic groups pack together to exclude water molecules

13 The Reaction between Antibody and Antigen Depends on the Binding Force Binding ForceCDRContact SiteReaction Too lowNo SpecCDRNo EpletNegative BorderlineIs SpecCDR insufficient? EpletNo binding? IntermediateSpecCDR is sufficient or requires a 2 nd CDR Eplet + 2 nd Contact Site Binding only StrongSpecCDR + 2 nd CDR + more CDR? Eplet + 2 nd Contact Site + more? Binding and conformational change of Fc to expose C1q binding site

14 Complementarity Determining Regions

15 “Seen” by A2,A68; B27,B44 “Seen” by A2,A68; B35,B44 Polymorphic Residues on B51 Structural Basis of a HLA-B51 Mismatch

16 B51 for A2,A68; B27,B44 B51 for A2,A68; B35,B44 ? ? How do antibodies react with structurally defined epitopes?

17 HLAMatchmaker-Based Analysis of Human Monoclonal Antibody Reactivity Demonstrates the Importance of an Additional Contact Site for Specific Recognition of Triplet-Defined Epitopes Rene J. Duquesnoy, Arend Mulder, Medhat Askar, Marcelo Fernandez-Vina and Frans H.J. Claas Human Immunology 66:

18 Two examples of mAbs: OK2H12: anti-62Qe OK4F9: anti-142mI Antibody Producer : A2,A68; B7,B27; Cw2,Cw7 Immunizer: A3 (pregnancy) 62Qe,142mI,144tKr,151aHe,163dT Triplets: 62Qe,142mI,144tKr,151aHe,163dT

19 Reactivity of mAb OK2H12 with 62Qe-carrying alleles

20 56G is the only residue shared between HLA-A3 and 62Qe-carrying alleles that react with OK2H12

21 Shared Polymorphic Amino Acids in the 62Qe-Defined Specificity Site Antibody Specificity Site Critical Second Contact Site

22 Shared Polymorphic Amino Acids in the 62Qe-Defined Specificity Site Antibody Specificity Site Critical Second Contact Site Distance between 56G and 62Q is 11 Angstroms, sufficient for contact by two different CDRs

23 Shared Polymorphic Amino Acids in the 62Qe-Defined Specificity Site Antibody Specificity Site Critical Second Contact Site is a Self Residue Distance between 56G and 62Q is 11 Angstroms, sufficient for contact by two different CDRs

24 62Qe,142mI,144tKr,151aHe,163dT Immunizing HLA-A3 Triplotype: 62Qe,142mI,144tKr,151aHe,163dT Two examples of mAbs: OK2H12: anti-62Qe OK4F9: anti-142mI

25 AlleleTriplets shared with HLA-A3N%Pos RxRx StrengthFlow BeadsElisa A* Qe, 142mI,144tKr,151aHe,163dT 7999%7.6++ A* Qe, 142mI,144tKr 48100% A* Qe, 142mI,144tKr 6897%7.8++ A* mI,151aHe 3797%7.5++ A* mI 16100%8.0++ A* Qe, 142mI 13100%8.0++ A* Qe, 142mI 1292%6.5nd A* Qe, 142mI 2997%7.6++ A* mI 1392%7.3++ A* mI 1275%6.3nd++ A* mI,151aHe 19100%8.0++nd A* mI,151aHe 7100%8.0nd++ A* mI,151aHe 8100%8.0++ A* Qe, 142mI 5100%8.0++ A* mI 170%1.0Neg A* mI,144tKr 788%1.6ndNeg A* mI,144tKr 425%1.7Neg A* mI,144tKr 50%1.0nd A* mI,151aHe 90%1.0Neg A* Qe, 142mI 220%1.0Neg A2/A28none676%1.3Neg LymphocytotoxicityAntigen-Binding Reactivity of mAb OK4F9 with 142mI-Carrying Alleles

26 The sequence 79G,80T,81L,82R,83G is shared between HLA-A3 and the 142mI-carrying alleles that react with OK4F9

27 Locations of 142mI-Defined Specificity and the 79GTLRG- Defined Critical Secondary Contact Sites on A*0301 Crtical Second Contact Site (Self Sequence) Antibody Specificity Site Distance between 142I and 82R is 13 Angstroms, Sufficient for contact by two different CDRs

28 Residue Polymorphisms and Reactivity of Bw6-Reactive SFR8-B6 Monoclonal Antibody Antibody Specificity site: 80N, 82R, 83G Critical contact site: 90A (about 11 Angstroms away) Permissive substitutions in 62 positions! Lutz et al. J. Immunol. 153: 4099, 1994 Studied the effect of single amino acid substitutions by mutagenesis of HLA-B7 molecules

29 Many Residue Substitutions Do Not Affect Reactivity With Antibody

30 Permissive Residue Substitutions that Do Not Inhibit Reactivity of the 62Qe-Specific mAb

31 Locations of Permissive Polymorphic Residues for 62Qe-Specific mAb Reactivity 62Qe 56G

32 Complement-Dependent Cytotoxic Antibody versus Non-Cytotoxic (Binding Only) Antibody

33 Serological Analysis of the HLA-A10 Complex “Monospecific” antisera against the HLA-A10 splits A25 and A26 (7 th Int. Workshop) Typing Serum Reaction with A25Reaction with A26 Anti-A25YesNo Anti-A26NoYes

34 Serological Analysis of the HLA-A10 Complex Duquesnoy and Schindler: Tissue Antigens 7: 65-73, 1976 Hackbarth and Duquesnoy: Transplant. Proc. 9: 43-45, 1977 Antisera against the HLA-A10 splits A25 and A26 Absorption studies: SerumReaction with A25Reaction with A26 Anti-A25CytotoxicityNo Cytotoxicity Only Binding Anti-A26No Cytotoxicity Only Binding Cytotoxicity Can HLAMatchmaker explain this?

35 Anti-A25 Serum Seru m HLA-type Ab Producer Ag Unshared Triplets JunA1,A3;B7.B8A25* Cytotoxic 80rIAlr, 150tAHe,156W, 183A, 193Av A26 Only Binding 150tAHe,156W,183A, 193Av * Immunizing Antigen

36 Seru m HLA-type Ab producer Ag Unshared Triplets MichA3,A23;B7,B13A26* Cytotoxic 76An, 90D, 150tAHe, 156W,163R,183A,193Av A25 Only Binding 90D,150tAHe,156W, 163R,183A,193Av Anti-A26 Serum *Immunizing Antigen

37 Anti-A10 Sera SerumHLA-type Ab Producer AgUnshared Triplets SandA1,A24;B7,B44A25* Cytotoxic 66rNv, 150tAHe,156W, 183A, 193Av A26 Cytotoxic 66rNv, 150tAHe,156W, 183A, 193Av ElliA1.A32;B13,B64A26* Cytotoxic 150tAHe,156W A25 Cytotoxic 150tAHe,156W * Immunizing Antigen

38 Immunizing A25 antigen Immunizing A26 antigen Anti-A25 Anti-A26 Antibody Specificity Site: 150tAhe Structural Basis of Cytotoxic Antibody Reactivity against A25 and A26 Critical Second Contact Site :82aLr Antibody Specificity Site: 150tAhe Critical Second Contact Site :76An The Critical Second Contact Site is a Non-Self Sequence and is Necessary for Complement Binding

39 Emerging Concepts The HLA antibody specificity site consists of a cluster of few polymorphic amino acids on the molecular surface –This site would be contacted by CDR-H3 Antibody reactivity may require a second contact site which is about 7-15 Angstroms away from the antibody specificity site –This site would be contacted by a different CDR

40 Interpretations of Negative Reactions of a Serum with HLA Antibodies 1.The mismatched HLA antigen has a different epitope not recognized by patient antibody: Acceptable mismatches are identified through sharing of epitopes not recognized by patient’s antibodies

41 Interpretations of Negative Reactions of a Serum with HLA Antibodies 1.The mismatched HLA antigen has a different epitope not recognized by patient antibody: Acceptable mismatches are identified through sharing of epitopes not recognized by patient’s antibodies 2.The mismatched HLA antigen carries the antibody specificity site but lacks the Critical Contact Site (CCS) for antibody binding: Acceptable mismatches are more difficult to identify

42 Interpretations of Negative Reactions of a Serum with HLA Antibodies 1.The mismatched HLA antigen has a different epitope not recognized by patient antibody: Acceptable mismatches are identified through sharing of epitopes not recognized by patient’s antibodies 2.The mismatched HLA antigen carries the antibody specificity site but lacks the Critical Contact Site (CCS) for antibody binding: Acceptable mismatches are more difficult to identify 3.Hidden polymorphisms may affect the conformation of surface residues in the antibody specificity site and/or critical second contact site

43 HLAMatchmaker Analysis of Antibody Reactivity Patterns with Luminex Single HLA Alleles Example: Screening for antibodies against HLA-DP

44 Anti- HLA-DP Reactivity of Serum Group B Pt 43, Patient types as DPB1*0201,-

45 Anti- HLA-DP Reactivity of Serum Group B Pt 43 Patient types as DPB1*0201,- Questions: Do the antibodies react with DPB or DPA or both ? What are the antibody specificities ? Which DP antigens are acceptable mismatches ? Which DP antigens are unacceptable?

46 HLAMatchmaker Analysis of Anti- HLA-DP Reactivity of Serum Group B Pt 43 (Step 1)

47 HLAMatchmaker Analysis of Anti- HLA-DP Reactivity of Serum Group B Pt 43 (Step 2)

48 HLAMatchmaker Analysis of Anti- HLA-DP Reactivity of Serum Group B Pt 43 (Step 3)

49 HLAMatchmaker Analysis of Anti- HLA-DP Reactivity of Serum Group B Pt 43 (Step 4)

50 Molecular Locations of Positions 84 and 87

51 84DE+87AV Corresponds to an Antibody-Defined Epitope

52 HLAMatchmaker-Predicted Unacceptable DPB Alleles

53 HLAMatchmaker-Predicted Acceptable DPB Alleles

54 HLAMatchmaker Determination of Unacceptable DPA Alleles

55 Predominant Eplets Reacting with anti-HLA-DP Antibodies * 55DE is similar to the 57DE eplet on DR11 All 55DE-reactive sera reacted also with DR11

56 Retransplant Candidates Have Donor-Specific Antibodies that React with Structurally Defined HLA-DR,DQ,DP Epitopes Duquesnoy et al. Transplant immunology, 18: , 2008

57 Three Groups of HLA-Sensitized Patients A.Sensitizing tissue is absent Previous transplant has been removed Prior transfusion and pregnancy B.Sensitizing tissue is present Transplanted organ still in place No evidence of pre-transplant sensitization C.Combination of A and B

58 * p=0.001 ** p< Incidence of Anti-HLA-DR, -DQ and -DP Antibodies in HLA Class II Sensitized Patients with or without a Transplant Present

59 Effect of eplet mismatching and the Incidence of antibodies to donor DRB1, DRB3, DRB4 and DRB5 mismatches

60 Eplet mismatching and the incidence of donor-specific anti-HLA-DQ antibodies

61 Frequencies of antibodies to donor DQB eplet mismatches

62 Frequencies of antibodies to donor DQA eplet mismatches

63 The Antibody Response to an HLA Mismatch is Restricted to a Small Number of Epitopes

64 Adeyi et al. Transplant Immunology, 14: 53-62, 2005 SERUM ANALYSIS AFTER TRANSPLANT NEPHRECTOMY REVEALS RESTRICTED ANTIBODY SPECIFICITY PATTERNS AGAINST STRUCTURALLY DEFINED HLA CLASS I MISMATCHES

65 0% 20% 40% 60% 80% 100% Before Tx Pre-AlloNx. Post-AlloNx Thirty Patients With Rejected Kidney Transplants Underwent Allograft Nephrectomy PRA Adeyi et al. Transplant Immunology, 14: 53-62, 2005

66 Donor Epitopes: A3: 62Qe,66rNv,70aQs,76Vd,80gTl,144tKr,149aAh,151aHe,163dT A31: 56R,62Qe,66rNv,74iD,76Vd,80gTl,193Av B55: 131S B63: 45Ma,66rNm,70aSa,74Y,131S Adeyi et al. Transplant Immunology, 14: 53-62, 2005

67 Donor Epitopes (serum-reactive epitopes are shown in underlined bold font) A3: 62Qe,66rNv,70aQs,76Vd,80gTl,144tKr,149aAh,151aHe,163dT A31: 56R,62Qe,66rNv,74iD,76Vd,80gTl,193Av B55: 131S B63: 45Ma,66rNm,70aSa,74Y,131S Adeyi et al. Transplant Immunology, 14: 53-62, 2005

68 Donor Epitopes (serum-reactive epitopes are shown in underlined bold font) A3: 62Qe,66rNv,70aQs,76Vd,80gTl,144tKr,149aAh,151aHe,163dT A31: 56R,62Qe,66rNv,74iD,76Vd,80gTl,193Av B55: 131S B63: 45Ma,66rNm,70aSa,74Y,131S Unacceptable epitopes identify unacceptable antigens e.g. 45Ma is present on B13, B46, B57,B62, B63. B75, B76, B76 Adeyi et al. Transplant Immunology, 14: 53-62, 2005

69 Donor Epitopes: B13: 41T,45Ma,76En, 80rTa,82aLr,144tQl,163E 82aLr is expressed by all Bw4-associated HLA-B antigens + A23, A24, A25 and A32 144tQl is unique for HLA-B13 After six months: the anti-76En and anti-82aLr antibodies have disappeared, Only anti-144tQl antibodies are detected Adeyi et al. Transplant Immunology, 14: 53-62, 2005

70 Relative Immunogenicity of Eplets How often do mismatched eplets induce specific antibodies? 14th International HLA Workshop Project Analysis of donor-specific antibodies in patients whose rejected kidney transplants had been removed

71 Preliminary Results: Eplet Immunogenicity in 62 Cases Duquesnoy, RJ and Claas FHJ: Progress Report of 14th International Histocompatibility Workshop Project on the Structural Basis of HLA Compatibility, Tissue Antigens, 69 (Suppl. 1): 1-5, 2007

72 15 th International Workshop Project on Epitope Immunogenicity Analyze post-allograft nephrectomy sera for antibodies against donor class I and class II epitopes Serum screening with single alleles (Luminex) and by CDC So far, 40 laboratories worldwide will contribute informative cases For more information go to

73 HLA Mismatch Immunogenicity Mismatched HLA antigens have different epitope loads HLA epitopes have different degrees of immunogenicity A better understanding of HLA immunogenicity will permit a permissible mismatch strategy for non-sensitized transplant patients

74 Use of HLAMatchmaker in Platelet Transfusions

75 HLAMatchmaker-Driven Analysis of Responses to HLA Typed Platelet Transfusions in Alloimmunized Thrombocytopenic Patients Ashok Nambiar, Rene J. Duquesnoy, Sharon Adams, Yingdong Zhao, Jaime Oblitas, Susan Leitman, David Stroncek and Francesco Marincola Department of Transfusion Medicine, National Institutes of Health Blood 107: , 2006

76 T R A N S F U S I O N P R A C T I C E Structural epitope matching for HLA-alloimmunized thrombocytopenic patients: a new strategy to provide more effective platelet transfusion support? Rene J. Duquesnoy Transfusion, 48: , February 2008

77 Alloimmunization-Induced Refractoriness to Random Donor Platelet Transfusions Antibody reactivity with –HLA Class I antigens –Platelet-specific antigens –Other antigens (MICA?, HLA class II?, blood groups) Refractory patients –Hematological defects (e.g. aplastic anemia) –Malignancies (e.g. leukemia) –Highly sensitized liver transplant candidates

78 Alloimmunization-Induced Refractoriness to Random Donor Platelet Transfusions Antibody reactivity with –HLA Class I antigens –Platelet-specific antigens –Other antigens (MICA?, HLA class II?, blood groups) Refractory patients –Hematological defects (e.g. aplastic anemia) –Malignancies (e.g. leukemia) –Highly sensitized liver transplant candidates

79 Treatment of HLA Alloimmunization- Induced Refractoriness Platelet transfusions from HLA matched donors (Yankee et al. N Eng J Med 281:1208, 1969) Platelet transfusions from donors mismatched for cross-reacting HLA antigens (Duquesnoy et al. Amer J Hematol 2: 219, 1977)

80

81 Serological Cross-Reactivity Between HLA Antigens HLA antigens carry “private” and “public” epitopes Cross-Reacting Groups (CREGs) of HLA antigens share the same public epitope Rodey and Fuller: Crit Rev Immunol 7:229, 1987

82 Duquesnoy et al. American Journal of Hematology. 2: , 1977

83

84 Responses to Platelet Transfusions with Different HLA Match Grades

85 Limitations of the Cross-Reactivity Based HLA Match Grade System Many BX matches are unacceptable epitope mismatches A and BU match groups may have incompatible epitopes revealed by 4-digit DNA typing CREG matching considers only HLA-A and HLA-B; how important is HLA-C?

86 Many BX Matches Have Incompatible Epitopes Cross-Reacting Matches and Bw4/Bw6 mismatches Eplet differences between Cross-Reacting Antigens Effect of BW4/6 incompatibility on responses to BX matched platelet transfusions Patients 1-8: lower increments Patients 9-21: comparable increments McElligott et al Blood 59: 971, 1982

87 Eplet Differences Between Cross-Reacting Antigens Example: A2 CREG

88 Limitations of the Cross-Reactivity Based HLA Match Grade System Many BX matches are unacceptable epitope mismatches A and BU match groups may have incompatible epitopes revealed by 4-digit DNA typing CREG matching considers only HLA-A and HLA-B; how important is HLA-C?

89 Eplet Differences Between 4-Digit Alleles

90 Limitations of the Cross-Reactivity Based HLA Match Grade System Many BX matches are unacceptable epitope mismatches A and BU match groups may have incompatible epitopes revealed by 4-digit DNA typing CREG matching considers only HLA-A and HLA-B. How important is HLA-C? –Not Important (Duquesnoy et al Transplant. Proc. 9: 1827, 1977) –Low expression on platelets (Mueller-Eckhart et al Tissue Antigens 16: 91, 1980) –Important for some patients (Saito et al Transfusion 42: 302, 2002)

91 HLA-C Eplets in Positions 1-193

92 Example of Luminex Screen for Antibodies Specific for HLA-C (1) What is the cut-off point to distinguish between positive and negative reactions?

93 Example of Luminex Screen for Antibodies Specific for HLA-C (2) Antibody react with Cw*0102 of donor Reactivity with donor’s Cw*0701? What HLA-C epitopes are recognized? Do HLAMatchmaker analysis What are the mismatched eplets?

94 Example of Luminex Screen for Antibodies Specific for HLA-C (3) These are the eplets on HLA-C alleles of donor and the panel Cw*1203 has no mismatched eplets for this patient One or more eplets on donor’s Cw*0102 must react with antibody Any reactivity with 65QNR of donor’s Cw*0701?

95 Example of Luminex Screen for Antibodies Specific for HLA-C (4) No reactivity with 65QNR of donor’s Cw*0701 No reactivity with the eplets of the negative alleles Cw*0202, Cw*0401, Cw*0501, Cw*1502, Cw*1701 and Cw*1801 Record these negative alleles in the HLAMatchmaker program

96 Example of Luminex Screen for Antibodies Specific for HLA-C (5) The 77TVS eplet of donor’s Cw*0102 is present on all reactive alleles 77TVS is an unacceptable mismatch

97 Example of Luminex Screen for Antibodies Specific for HLA-C (6)

98 Proposed HLA Epitope-Based Matching Protocol (steps 1 and 2) 1.Perform HLA-A, B, C typing of patients and donors by DNA methods at the high-resolution (4-digit allele) level. 2.Screen patient sera with HLA typed panel –Complement-dependent methods: direct and/or antiglobulin-augmented lymphocytotoxicity –Antigen-binding assays such as Luminex, Flow Cytometry and ELISA preferably with single HLA class I alleles –HLAMatchmaker-based analysis of serum reactivity pattern to identify acceptable mismatches

99 Proposed HLA Epitope-Based Matching Protocol (step 3) 3. Conduct a platelet donor search –Establish a computerized platelet donor registry that incorporates an HLAMatchmaker-based search engine –Enter the HLA type of the patient and the non- reactive mismatched alleles in this database and the computer will generate a list of donors with matches and acceptable mismatches at the eplet level –No need for platelet cross-match testing for HLA incompatibility

100 Proposed HLA Epitope-Based Matching Protocol (step 4) 4. Evaluate the outcome of the platelet transfusion, if increment is low then: –Determine whether serum reactivity patterns have improperly been interpreted in terms of HLA mismatch acceptability –Look for antibodies against platelet-specific antigens and blood groups, or autoimmune phenomena and drug reactions –Consider clinical conditions such as coagulopathy, infection and hepatosplenomegaly

101 Prevention or Delay of HLA Alloimmunization 1.HLAMatchmaker-based selection of apheresis platelets with minimal numbers of mismatched eplets –From existing inventories of stored platelets –Do a computer search for compatible platelet donor –Avoid immunogenic eplets 2.Leukoreduction of platelet preparations prior to transfusion

102 Prevention or Delay of HLA Alloimmunization 1.HLAMatchmaker-based selection of apheresis platelets with minimal numbers of mismatched eplets –From existing inventories of stored platelets –Do a computer search for compatible platelet donor –Avoid immunogenic eplets 2.Leukoreduction of platelet preparations prior to transfusion

103 Prevention or Delay of HLA Alloimmunization 1.HLAMatchmaker-based selection of apheresis platelets with minimal numbers of mismatched eplets –From existing inventories of stored platelets –Do a computer search for compatible platelet donor –Avoid immunogenic eplets 2.Leukoreduction of platelet preparations prior to transfusion

104 Conclusions The serological cross-reacting antigen matching system introduced in 1977 should be replaced by a system that incorporates modern concepts of epitope reactivity with antibody. The proposed HLA epitope matching protocol is expected to benefit platelet transfusion outcome and increase the number of compatible donors for refractory patients.

105 Introductory articles and tutorials HLAMatchmaker related publications –From UPMC –From other institutions Free downloads of all programs –Class I and class II matching –Antibody analysis –Other programs Contacts and communications New Website

106 If you would like to discuss HLAMatchmaker in Pittsburgh, come visit me in my office…

107 on the Allegheny River


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