histocompatibility testing and organ sharing · 2016. 8. 2. · histocompatibility testing and...

8

Histocompatibility Testingand Organ Sharing

Histocompatibility and its current application in kidney trans-plantation are discussed. Both theoretic and clinical aspects ofhuman leukocyte antigen testing are described, including anti-

gen typing, antibody detection, and lymphocyte crossmatching. Livingrelated, living unrelated, and cadaveric donor-recipient matching algo-rithms are discussed with regard to mandatory organ sharing andgraft outcomes.

Lauralynn K. Lebeck Marvin R. Garovoy

C H A P T E R

8.2 Transplantation as Treatment of End-Stage Renal Disease

A

Chromosome 6(short arm) Class II Class III Class I HLA complex

Glyoxylase DP

DZ DO Cyp21 TNF

DQ DR B C A

FIGURE 8-1

The major histocompatibility complex (MHC) is a group of closelylinked genes that was first appreciated because it was found to contain the structural genes for transplantation antigens. A, TheMHC, located on the short arm of chromosome 6, is now recog-nized to include many other genes important in the regulation ofimmune responses. B, Regions of the MHC classes I, II, and III.The MHC can be divided into three regions, of which the class Iand II regions contain the loci for the human histocompatibilityantigen or human leukocyte antigen (HLA). Genes in the class I

B

Class II

0

1500

500 3000

1000

DPA

1D

PA2

DPB

1D

PB2

DN

A

DM

BD

MA

LMP

2T

AP

1LM

P 7

TA

P 2

DQ

B2

DQ

B1D

QA

1

DQ

A2

DR

B

DR

A

B C X E J A H G F

CY

P 21

-BC

4B

CY

P 21

-A

C4A

BF C2 H

SP 7

0

TN

F α

TN

F β

2000 3000 4000

Class III Class I

Specific locus

w 8

The major histocompatibilitycomplex in humans

Provisionalspecificity

Specific antigen

Allele designation

Specific alleleCorresponding antigen

Locus

HLA

HLA DRB1 * 04 03

C

FIGURE 8-2

Nomenclature of human leukocyte antigen (HLA) specificities. HLAnomenclature may be confusing to the newcomer, but the format islogical. The prefix HLA precedes all antigens or alleles to definethe major histocompatibility complex (MHC) of the species. Thedesignation, A, B, C, DR, and so on, is next and defines the locus.The locus is followed by a number that denotes the serologicallydefined antigen or a number with an asterisk that denotes the molecularly defined allele. In some cases the letter w is placedbefore the serologic antigen, indicating it is a workshop designationand the specific assignment is provisional.

region encode the a or heavy chain of the class I antigens, HLA-A,B, and C. The class I region is composed of other genes, most ofwhich are pseudogenes and are not expressed. The MHC class IIregion is more complex, with structural genes for both the a and b chains of the class II molecules. The class II region includes fourDP genes, one DN gene, one DO gene, five DQ genes, and a vary-ing number of DR genes (two to 10), depending on the halotype.Many other immune response genes are coded within the class IIIregion. TNF—tumor necrosis factor.

8.3Histocompatibility Testing and Organ Sharing

PRETRANSPLANTATIONTESTING FOR RENAL PATIENTS

HLA phenotype

Patient cells tested with known antisera

HLA antibody screen

Known cells tested with patient sera

HLA crossmatch

Donor cells tested with patient sera

FIGURE 8-3

In an immunogenetics and transplantation laboratory, three major types of renal pretrans-plantation testing are performed routinely. The human leukocyte antigen (HLA) assignmentsare assigned by serologic methods (ie, complement-dependent cytotoxicity); however, molec-ular-based methodologies are becoming widely accepted. Most laboratories now have thecapability of reporting at least low-resolution molecular class II types.

The sera of patients awaiting cadaveric donor kidney transplantation are tested for thedegree of alloimmunization by determining the percentage of panel reactive antibodies(PRAs). Current federal regulations require that the serum screening test use lymphocytesas targets; however, because these same regulations no longer mandate monthly screening,assays using soluble antigens may be used as adjuncts to the classic lymphocytotoxic assays.

The purpose of cross-match testing is to detect the presence of antibodies in the patients’serum that are directed against the HLA antigens of the potential donor. When present,the antibodies indicate that the immune system of the recipient has been sensitized to thedonor antigens. The various test methods differ in sensitivity, including the multiple variationsof the lymphocytotoxicity text, flow cytometry, and enzyme-linked immunosorbent assay(ELISA). The degree of acceptable risk is one factor to be considered in selecting a methodof appropriate sensitivity. For example, when the only risk considered unacceptable is thatof hyperacute rejection, a technique having lower sensitivity is adequate. A second approachmay be to consider the degree to which an individual patient or type of patient is at riskfor graft rejection. The patient having a repeat graft is at higher risk for graft rejectionthan is the patient receiving a primary graft. Because patients differ in their degree of risk,it is appropriate to use different techniques to offset that risk.

MHC I AND II CHARACTERISTICS

Class I

Composed of HLA-A, -B, and -C

Ubiquitous distribution

Autosomal codominant

Target for immune effector mechanism

Serologic and molecular detection

Heterodimer noncovalently linked

Heavy chain (a):

Contains variable regions

Confers human leukocyte antigen specificity

Light chain (b2-microglobulin):

Invariant

Class II

Composed of HLA-DR, -DQ, and -DP

Restricted distribution

Autosomal codominant

Major role in immune response induction

Serologic, molecular, and cellular detection

Heterodimer noncovalently linked

a Chain:

Nonvariable in HLA-DR

Contains variable regions in HLA-DQand -DP

b Chain:

Contains variable regions

Confers most of HLA-DR specificity

FIGURE 8-4

Human leukocyte antigens (HLAs) are heterodimeric cell-surfaceglycoproteins. HLAs are divided into two classes, according totheir biochemical structure and respective functions. Class I antigens(A, B, and C) have a molecular weight of approximately 56,000 Dand consist of two chains: a glycoprotein heavy chain (a) and alight chain (b2-microglobulin). The a chain is attached to the cellmembrane, whereas b2-microglobulin is associated with the achain but is not covalently bonded. The HLA class I molecules arefound on almost all cells; however, only vestigial amounts remainon mature erythrocytes. Class II antigens (HLA-DR, DQ, and DP)have a molecular weight of approximately 63,000 D and consist oftwo dissimilar glycoprotein chains, designated a and b, both ofwhich are attached to the membrane. Each chain consists of twoextramembranous amino acid domains, and the outer domains ofeach molecule contain the variable regions corresponding to class IIalleles. Although class I antigens are expressed on all nucleated cellsof the body, the expression of class II antigens is more restricted. ClassII antigens are found on B lymphocytes, activated T lymphocytes,monocyte-macrophages, dendritic cells, and early hematopoieticcells, and of importance in transplantation, endothelial cells.


A

MHCprotein

T-cellreceptor

α chain

β chainProcessedantigen

FIGURE 8-5

Biology of the major histocompatibility complex (MHC). A, Thebiologic function of MHC antigens is to present antigenic peptidesto T lymphocytes. In fact, it is an absolute requirement of T-lym-phocyte activation for the T cells to “see” the antigenic peptidebound to an MHC molecule. This MHC restriction has beendefined on a molecular basis with the elucidation of the crystallinestructures of classes I and II MHC molecules. B, The N-terminaldomains of the MHC molecules are formed by the folding of por-tions of their component chains in b-pleated sheets and a helices.C, The sheet portions form a floor, and the helices form the sidesof a peptide-binding groove.

α1 α2

β2m α3

B C

A

Peptide

β2m subunitHeavysubunit

B

Peptide

β subunitα subunit

FIGURE 8-6

The structure of class I and II molecules.Comparison of the crystalline structures ofclasses I and II molecules has revealed overallstructural similarity, with a few significantdifferences. A, Class I molecules have agroove with deep anchor pockets at eachend (a “pita pocket”). These pockets restrictthe binding of peptides to those of eight tonine amino acid residues in length. B, Thepeptide-binding groove of class II moleculesis more flexible and relatively open at oneend, more like a “hotdog bun,” permittinglarger peptides from 13 to 25 amino acidresidues in length to bind.


FIGURE 8-7

Allelic polymorphism. Allelic polymorphismis a hallmark of the human leukocyte antigen(HLA) system. The extreme polymorphism ofthe HLA system is seen in the large numbersof different alleles that exist for the multiplemajor histocompatibility complex (MHC)loci. At any given locus, one of severalalternative forms or alleles of a gene canexist. Because so many alleles are possiblefor each HLA locus, the system is extremelypolymorphic. The currently accepted WorldHealth Organization serologically definedalleles are shown here. Established HLAantigens are designated by a number followingthe letter that denotes the HLA locus (eg,HLA-A1 and HLA-B8). For example, byserologic techniques, 28 distinct antigensare recognized at the HLA-A locus, and 59 defined antigens at the HLA-B locus.Sequencing studies of the HLA-DRB1 genehave identified over 100 distinct alleles, andpreliminary analysis indicates that this levelof polymorphism will be as high for otherloci such as HLA-B. MHC polymorphismensures effective antigen presentation ofmost pathogens; however, clinically, MHCpolymorphism complicates attempts to findhistocompatible donors for solid organtransplantation.

HLA SPECIFICITIES

A

A1

A2

A203

A210

A3

A9

A10

A11

A19

A23(9)

A24(9)

A2403

A25(10)

A26(10)

A28

A29(19)

A30(19)

A31(19)

A32(19)

A33(19)

A34(10)

A36

A43

A66(10)

A68(28)

A69(28)

A74(19)

A80

B

B5

B7

B703

B8

B12

B13

B14

B15

B16

B17

B18

B21

B22

B27

B2708

B35

B37

B38(16)

B39(16)

B3901

B3902

B40

B4005

B41

B42

B44(12)

B45(12)

B46

B47

B48

B49(21)

B50(21)

B

B51(5)

B5102

B5103

B52(5)

B53

B54(22)

B55(22)

B56(22)

B57(17)

B58(17)

B59

B60(40)

B61(40)

B62(15)

B63(15)

B64(14)

B65(14)

B67

B70

B71(70)

B72(70)

B73

B75(15)

B76(15)

B77(15)

B7801

B81

Bw4

Bw6

C

Cw1

Cw2

Cw3

Cw4

Cw5

Cw6

Cw7

Cw8

Cw9(w3)

Cw10(w3)

DR

DR1

DR103

DR2

DR3

DR4

DR5

DR6

DR7

DR8

DR9

DR10

DR11(5)

DR12(5)

DR13(6)

DR14(6)

DR1403

DR1404

DR15(2)

DR16(2)

DR17(3)

DR18(3)

DR51

DR52

DR53

DQ

DQ1

DQ2

DQ3

DQ4

DQ5(1)

DQ6(1)

DQ7(3)

DQ8(3)

DQ9(3)

DP

DPw1

DPw2

DPw3

DPw4

DPw5

DPw6

Antigens listed in parentheses are the broad antigens, antigens followed by broad antigens in parentheses are the antigen splits.


Father Mothera b c d

A1 A3 A2 A9

Cw7 Cw7 Cw7 Cw4B8 B7 B12 B35

DR3 DR2 DR5 DR3

Childrena c a d

A1 A2 A1 A9


DR3 DR5 DR3 DR3

b c b dA3 A2 A3 A9


DR2 DR5 DR2 DR3

Wash × 3

Add AHG 2 min

Stage 1

Stage 2

Stage 3

Add rabbit serum(complement)

30 minRT

60 minRT

Visualize membrane injury(Eosin-y, AO/EB, etc.)

Incubate cellsand serum

FIGURE 8-8

Genetic principles of the major histocompatibility complex (MHC).The MHC demonstrates a number of genetic principles. Each personhas two chromosomes and thus two MHC haplotypes, each inheritedfrom one parent. Because the human leukocyte antigen (HLA) genesare autosomal and codominant, the phenotype represents the combined expression of both haplotypes. Each child receives onechromosome and hence one haplotype from each parent. Becauseeach parent has two different number 6 chromosomes, four differentcombinations of haplotypes are possible in the offspring. Thisinheritance pattern is an important factor in finding compatiblerelated donors for transplantation. Thus, an individual has a 25%chance of having an HLA-identical or a completely dissimilar siblingand a 50% chance of having a sibling matched for one haplotype.The genes of the HLA region occasionally (≈ 1%) demonstratechromosomal crossover. These recombinations are then transmittedas new haplotypes to the offspring.

FIGURE 8-9

Complement-dependent technique. The standard technique used todetect human leukocyte antigen (HLA)-A, -B, -C, -DR, and -DQ anti-gens has been the microlymphocytotoxicity test. This assay is a com-plement-dependent cytotoxicity (CDC) in which lymphocytes are usedas targets because the HLA antigens are expressed to varying degreeson lymphocytes and a relatively pure suspension of cells can beobtained from anticoagulated peripheral blood. Lymphocytes obtainedfrom lymph nodes or the spleen also may be used. HLA antisera ofknown specificity are placed in wells on a “Terasaki microdroplettray.” A concentrated suspension of lymphocytes is added to eachwell. If the target lymphocytes possess the antigen corresponding tothe antibody present in the antiserum, the antibody will affix to thecells. Rabbit complement is then added to the wells and, when suffi-cient antibody is bound to the lymphocyte membranes, complement isactivated. Complement activation injures the cell membranes (lympho-cytotoxicity) and increases their permeability. Cell injury is detected bydye exclusion: cells with intact membranes (negative reactions)exclude vital dyes; cells with permeable membranes (positive reac-tions) take up the dye. Sensitivity of the CDC assay is increased bywash techniques or the use of AHG reagents prior to the addition ofcomplement. Because HLA-DR and -DQ antigens are expressed on B cells and not on resting T cells, typing for these antigens usuallyrequires that the initial lymphocyte preparation be manipulated beforetesting to yield an enriched B-cell preparation. AHG—antiglobulin-augmented lymphocytotoxicity; RT—room temperature.

SCORING OF COMPLEMENT-DEPENDENTCYTOTOXICITY REACTIONS

Assigned value

1

2

4

6

8

0

Dead cells, %

0–10

11–20

21–50

51–80

80–100

Unreadable

Interpretation

Negative

Borderline negative

Weak positive

Positive

Strong positive

No cells, contamination, bubble

FIGURE 8-10

Scoring of complement-dependent cytotoxicity. In an effort to standardize interpretation of complement-dependent cytotoxicity(CDC) reactions, a uniform set of scoring criteria have been estab-lished. When most of the cells are alive, visually refractile onmicroscopic examination, a score of 1 is assigned. Conversely,when most of the cells are dead, a score of 8 is assigned. Thismethod of interpretation for CDC reactions is universally used incross-match testing, antibody screening, and antigen phenotypingfor serologically defined HLA-A, -B, -C, -DR, and -DQ. (Adaptedfrom Gebel and Lebeck [1]; with permission.)


1

2

34

5

6 7

8

9

10

11

FIGURE 8-11

The United Network for Organ Sharing (UNOS) regions. UNOS isa not-for-profit corporation within the United States organizedexclusively for charitable, educational, and scientific purposesrelated to organ procurement and transplantation. Its formationestablished a national Organ Procurement and TransplantationNetwork with the mandate to improve the effectiveness of thenation’s renal and extrarenal organ procurement, distribution, andtransplantation systems by increasing the availability of and accessto donor organs for patients with end-stage organ failure. Additionally,the UNOS maintains quality assurance activities and systematicallygathers and analyzes data and regularly publishes the results of thenational experience in organ procurement and preservation, tissuetyping, and clinical organ transplantation. Functionally, the UnitedStates is divided into UNOS regions as detailed on this map.Additional geographic divisions (ie, local designation) defined bythe individual organ procurement organizations and the transplan-tation centers they service comprise the working system for cadav-eric renal allocation.

UNITED NETWORK FOR ORGAN SHARING: NUMBER OF PATIENT REGISTRATIONS ON THE NATIONAL TRANSPLANT WAITING LIST AS OF OCTOBER 31, 1997

Kidney numberby blood type (%)

Type O: 19,654(52.04)

Type A: 10,612(28.10)

Type B: 6579(17.42)

Type AB: 923(2.44)

Total: 37,768

Kidney numberby race (%)

White: 18,353(48.59)

Black: 13,290(35.19)

Hispanic: 3441(9.11)

Asian: 2200(5.83)

Other: 484(1.28)

Total: 37,768

Kidney numberby gender (%)

Female: 16,269(43.08)

Male: 21,499(56.92)

Total: 37,768

Kidney number by transplantation center region (%)

Region 1: 1738(4.60)

Region 2: 6060(16.05)

Region 3: 3844(10.18)

Region 4: 2191(5.80)

Region 5: 7361(19.49)

Region 6: 855(2.26)

Region 7: 3826(10.13)

Region 8: 1559(4.13)

Region 9: 3936(10.42)

Region 10: 3121(8.26)

Region 11: 3277(8.68)

Total: 37,768

Kidney number by age (%)

0–5: 76(0.20)

6–10: 119(0.32)

11–17: 429(1.14)

18–49: 21,102(55.87)

50–64: 12,942(34.27)

65+: 3100(8.21)

Tota: 37,768

FIGURE 8-12

The United Network for Organ Sharing (UNOS) patient waitinglist. The UNOS patient waiting list is a computerized list ofpatients waiting to be matched with specific donor organs in thehope of receiving a transplantation. Patients on the waiting listare registered on the UNOS computer by UNOS member trans-plantation centers, programs, or organ procurement organiza-tions. The UNOS Match System is an algorithm used to prioritize

patients waiting for organs. The system eliminates potential recipients whose size or ABO type is incompatible with that of a donor and then ranks those remaining potential recipientsaccording to a UNOS board-approved system. As indicated here, nearly 40,000 patients are awaiting kidney transplantationin the United States. (Adapted from the United Network forOrgan Sharing [2]).


FIGURE 8-13

Point system for kidney allocation. Kidneysthat cannot be allocated to a human leuko-cyte antigen (HLA)–matched patient aredistributed locally to candidates who areranked according to waiting time, withadditional points for degrees of HLA mis-match and antibody sensitization. Pediatricpatients, medically urgent cases, and previousdonors (living related donors, and so on)also are given a point advantage.

POINT SYSTEM FOR KIDNEY ALLOCATION

Time of waiting

The “time of waiting” begins when a patient is listed and meets the minimum established criteria on the UnitedNetwork for Organ Sharing Patient Waiting List. One point will be assigned to the patient waiting for the longestperiod, with fractions of points being assigned proportionately to all other patients according to their relativetime of waiting.

Quality of HLA mismatch

10 points if there are no A, B, or DR mismatches.

7 points if there are no B or DR mismatches.

5 points if there is one B or DR mismatch.

2 points if there is a total of two mismatches at the B and DR loci.

Panel reactive antibody

Patients will be assigned 4 points if they have a panel reactive antibody level of 80% or more.

Medical urgency

No points will be assigned to patients based on medical urgency for regional or national allocation of kidneys.Locally, the patient’s physician has the authority to use medical judgment in assignment of points for medicalurgency. When there is more than one local renal transplantation center, a cooperative medical decision isrequired before assignment of points for medical urgency.

Pediatric kidney transplantation candidates

4 points if the patient is under 11 years of age.

3 points if the patient is over 11 and under 18 years of age.

CROSSMATCH METHODS

Lymphocytotoxicity:

Auto–crossmatch vs allo–crossmatch

T or B cell

Short/long/wash/AHG methods

IgG vs IgM

Flow cytometry

Enzyme-linked immunosorbent assay

FIGURE 8-14

Crossmatch methods. Early reports correlating a positive crossmatch between recipientserum and donor lymphocytes with hyperacute rejection of transplanted kidneys led toestablishing tests of recipient sera as the standard of practice in transplantation. However,controversy remains regarding 1) the level of sensitivity needed for crossmatch testing; 2) the relevance of B-cell crossmatches, a surrogate for class II incompatibilities; 3) the relevance of immunoglobulin class and subclass of donor-reactive antibodies; 4) the significanceof historical antibodies, ie, antibodies present previously but not at the time of transplantation;5) the techniques and type of analyses to be performed for serum screening; and 6) theappropriate frequency and timing of serum screening. Despite a number of variables, whenthe data from reported studies are considered collectively, several observations can bemade. Human leukocyte antigen–donor-specific antibodies present in the recipient at thetime of transplantation are a serious risk factor that significantly diminishes graft functionand graft survival. Antibodies specific for human leukocyte antigen class II antigens (HLA-DRand -DQ) are as detrimental as are those specific for class I antigens (HLA-A, -B, and -C). Thedegree of risk resulting from HLA-specific antibodies varies among immunoglobulin classes,with immunoglobulin G antibodies representing the most serious risk. AHG—antiglobulin-augmented lymphocytotoxicity.


A

SSC

250

200

150

100

50

00 50 100 150 200 250

FSC

R1

∝ Human IgG-Fc-FITCC

Cou

nts

200

160

120

80

40

00 50 100 150 200 250

T cell

M1

D

100

90

80

70

60

50

40

300 6 12 0 6 12

Months after transplantation

Neg (n = 508)

Pos (n = 106)

Neg (n = 75)

Pos (n = 43)

First Regraft

B

CD

3 PE

250

200

150

100

50

00 50 100 150 200 250

FSC

R2

FIGURE 8-15Techniques of crossmatch testing. Early crossmatch testing provided a means to preventmost but not all hyperacute rejections. These early tests were performed with a techniqueof rather low sensitivity. Subsequently, more sensitive techniques were employed in anattempt to not only prevent all hyperacute rejections but also improve graft survivalrates. Techniques that have been used include variations of the lymphocytotoxicity testthat incorporate wash steps, change in incubation times or temperatures, or both, or addan antiglobulin reagent. Flow cytometry and an array of other methods such as antibody-

ALTERNATIVE APPROACHES TO HLA MATCHING

CREG*

1C

2C

5C

7C

8C

12C

4C

6C

Associated human leukocyteantigen gene products

A1,3,9,10,11,28,29,30,31,32,33

A2,9,28, B17

B5,15,17,18,35,53,70,49

B7,13,22,2740,41,47,48

B8,14,16,18

B12,13,21,40,41

A24,25,32,34, Bw4

Bw6, Cw1,3,7

Approximate “epitope” frequency, %

80

66

59

64

37

44

85

87

C refers to major public epitope or cross-reactive groups (CREG).

FIGURE 8-16Alternative approaches to human leukocyte antigen (HLA) matching.Because completely mismatched kidney transplantations function well over long periods, an alternative approach might begin with thehypothesis that six-antigen “mismatched” transplantations were notcompletely mismatched. Interest in reevaluating the potential roles of cross-reactive groups (CREGs) in transplantation is one suchapproach. In the early days of serologic HLA testing, a high panelreactive antibody sera was considered to be composed of many anti-HLA antibodies. It was later noted, however, that sera of highly sensi-tized patients awaiting solid organ transplantation were generally com-posed of a small number of antibodies directed at public antigens, alsocalled CREGs, rather than multiple antibodies, each reacting with aspecific conventional HLA antigen. Furthermore, the frequency of theCREGs was much higher, eg, 35% to 88%, than that of even the mostcommon HLA-A and -B antigens. By inference, therefore, matching fordonor and recipient antigens included in the same CREG, ie, CREGmatching, could result in a higher number of matched transplantationsand a lower level of sensitization in patients having repeat grafts. Inaddition, because of the inclusion of several private HLA-A and -Bantigens within a single CREG, a number of relatively rare antigenscan be matched more easily, offering the possibility of improved graftsurvival for a greater number of both white and nonwhite patients.(Adapted from Thelan and Rodey [4]; with permission.)

dependent cellular cytotoxicity also havebeen tried. Two of the most sensitive tech-niques are the antiglobulin-augmented lym-phocytotoxicity (AHG) and flow cytomet-ric crossmatching. A, The use of flowcytometry to define the lymphocyte popu-lation by light scatter parameters, followedby a specific marker for T lymphocytes, ie, CD3 (B) allows this technique to behighly specific for human leukocyte antigen(HLA) class I–positive cells. The donorlymphocytes have been preincubated withrecipient serum, washed, and subsequentlystained with AHG-Fluorescsin isothio-cyanate (FITC), a fluorochrome-labeledantihuman globulin. C, Results of flowcytometric cross-matching are evaluated asshifts in the fluorescence from negative seraand are interpreted as positive or negativebased on independently defined cutoffsabove the negative. D, Multiple studies inrenal transplantation have shown correla-tions between positive AHG or flow cyto-metric cross-matches and decreased graftsurvival at 1 year or more. The largest differences are seen when patients aregrouped as primary grafts versus repeatgrafts. In some instances the effect of usinga more sensitive cross-match techniqueonly can be seen in patients having repeatgrafts or those with a higher immunologicrisk. CD3 PE—monoclonal antibody toCD3 fluorescent labelled with phycoery-thrin; FC—constant fragment of IgG mole-cule; FITC—fluorescent labelled with fluo-rescein isothiocynate; FSC—forward scat-ter; R1—region 1; R2—region 2; SSC—sidescatter. (Panel D adapted from Cook [3];with permission.)


A

100

80

60

40

30

20

100 1 2 3 4 5 6 7 8 9 10

Years after transplantation

Gra

ft s

urvi

val (

log)

, %

White1st cadaverUNOS (1991–1996)

ABDRMM

0

1

2

3

4

5

6

n

3023

1305

3736

6312

6414

3641

1209

T 1⁄2

14

12

12

12

11

11

10

B

100

80

60

40

30

20

10

Black1st cadaverUNOS (1991–1996)

0 1 2 3 4 5 6 7 8 9 10


Gra

ft s

urvi

val (

log)

, % ABDRMM

0

1

2

3

4

5

6

n

301

255

970

2459

3251

2078

739

T 1⁄2

7

7

6

6

6

6

6

FIGURE 8-17

The role of human leukocyte antigen (HLA) matching in the UnitedStates in whites (A) and blacks (B). Recent large registry analysesof the role for HLA matching in renal transplantation consistentlyhave shown a stepwise decrease in long-term graft survival rateswith increasing antigen mismatches. Based on these results the UnitedNetwork of Organ Sharing (UNOS) incorporated the level of HLAmatch into its algorithm used nationally for kidney allocation. TheUNOS initially determined that transplantations for which all sixHLA-A, -B, and -DR antigens matched in the donor and recipientshould be performed. Each cadaveric donor type was compared by acomputer search with the HLA types of all patients awaiting kidneytransplantation. When a patient with six antigen matches was

identified in an ABO-compatible recipient, the kidney was offeredfor that patient, and if accepted by the transplantation center, wasshipped for transplantation. (Normally, kidneys from a patientwith blood type O are allocated only to patients with type O blood,except in the case of patients with six antigen matches.) The UNOSpolicy regarding mandatory sharing of HLA-matched kidneys hasbeen liberalized twice. The first time was in 1990 to include pheno-typically matched pairs with fewer than six antigens. The policywas changed for a second time in 1995 to include zero-mismatchedpairs in which the donor could have fewer antigens than the recipient,provided none were mismatched. (Adapted from Cecka [5]; withpermission.)

HLA-DR13

HLA-DR14

*1301–*1312 *1314–*1330

*1401, *1402, *1405–*1429

HLA-DR6

DR1403DR1404

Serology(antibody defined)

Molecular(Low Intermediate High resolution)

versus

FIGURE 8-18

Serologic testing and antigen assignment. Most of the publishedtransplantation outcome data is based on serologic testing andassignment of antigens. These data include algorithm matchingbased on “broad” human leukocyte antigen (HLA) specificitiessuch as HLA-DR6 that includes HLA-DR13 and HLA-DR14 andtheir many alleles. The question has now become one of what levelof HLA testing is useful clinically for matching purposes in renaltransplantation. Although this issue has not been resolved, recentdata published from the European Registry upholds the positiveeffect that “correct” HLA matching has had on renal graft outcome.


A

Gra

ft s

urvi

val,

%100

90

80

70

60

50

400 3 6 9 12

Time, mo

DNA: DR 0 mm(n = 64)

DNA: DR >0 mm(n = 22)

B

Gra

ft s

urvi

val,

%

100

90

80

70

60

50

00 3 6 9 12

Time, mo

DNA: A+B 0 mm(n = 183)

DNA: A+B >0 mm(n = 32)

FIGURE 8-19

Classes II and I mismatches in supposed 0 mm shared renal transplantations. The effect ongraft survival of shared human leukocyte antigen (HLA) 0mm organs when defined by sero-logic typing and then confirmed by molecular typing. A strong effect of HLA matching isseen at even 1 year on the graft survival. A, Eighty-six first cadaveric kidney transplantationsthat were reported by serologic typing as HLA-A, -B, -DR “identical-compatible” were testedby molecular methods. Sixty-four transplantations were confirmed to be HLA-DR compati-ble; however, mismatches were found in the remaining 22 transplantations. Transplantationsin which HLA compatibility was confirmed had a functional success rate of 90% at 1 yearcompared with 68% for transplantations in which the DNA typing revealed HLA-DR mis-matches (P < 0.02). B, An analysis of the influence of HLA-class I DNA typing on kidneygraft survival is shown. A total of 183 cadaveric transplantations were confirmed to beHLA-A and B compatible after DNA typing, whereas mismatches were found in the remain-ing 32 cases. Transplantations in which compatibility was confirmed had a functional successrate of 86.9% at 1 year compared with a 71.9% rate for those in which DNA typingrevealed HLA-A or -B mismatches (P = 0.033.) (Panel A adapted from Opelz and coworkers[6]; panel B adapted from Mytilineous and coworkers [7]; with permission.)

A

100

80

90

70

50

0

60

40

30

20

10

0 1 2 3 4 5 6 7 8


Gra

ft s

urvi

val,

%

88

89

90

91

n

1809

1895

2086

2385

t 1⁄2

12.5

14.3

14.9

14.6

Living donor

92

93

94

95

n

2527

2828

2914

3117

t 1⁄2

17.0

16.3

17.5

8.8

B

50

0

60

40

30

20

10

Parent Offspring Sibling Otherrelative

Spouse/otherunrelated

%

1988

1996

FIGURE 8-20

Living donor kidney transplantation graft survival rates (A) anddonor sources (B). The high graft survival rates reported for recipients of living donor kidneys improved from 89% in 1988 to 93% in 1991 (P < 0.001), even though a substantial increasehas occurred in both the number of living donors and centersperforming these transplantations. Some of the increase in livingdonations has been due to a growing acceptance of so-called

unconventional donors, ie, spouses and other genetically unrelated donors, as well as distant relatives and half-siblings. In 1988–1989, unrelated donors accounted for 4% of livingdonor transplantations and distant relatives for 2%. These numbers have tripled and are now at 12% and 6%, respectively.(Panel A from Cecka [8]; panel B adapted from the UnitedNetwork for Organ Sharing [9]; with permission.)


References

1. Gebel HM, Lebeck LK: Crossmatch procedures used in organ transplantation. Clin Lab Med 1991, 11:609.

2. United Network for Organ Sharing: UNOS Bulletin 1997, 2.

3. Cook DJ, et al.: An approach to reducing early kidney transplant failure by flow cytometry crossmatching. Clin Transpl 1987, 1:25.

4. Thelan D, Rodey G: American Society of Histocompatibility andImmunogenetics Laboratory Manual, edn 3. Lenexa, KS: ASHI.

5. Cecka JM: The role of HLA in renal transplantation. HumanImmunology 1997, 56:6–16.

6. Opelz et al.: Transplantation 1998, 55:782–785.

7. Mytilenous et al.: Tissue Antigens 1997, 50:355–358.

8. Cecka JM: UNOS Scientific Renal Transplant Registry. In ClinicalTransplant Registry. Edited by Cecka JM, Terasaki P. Los Angeles:UCLA; 1996:1–14.

9. United Network for Organ Sharing: UNOS Bulletin 1997, 2.

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