22-6-12 part 1

Humoral Rejection

Henny OttenDepartment of Immunology

HLA Class-I and -II

Binding of peptides to HLA

HLA-restriction

Polymorphism of HLA atpositions near interaction withTCR and peptide

S. Marsh, 2008

Polymorphism of HLA

Frequency of alleles

Many allele variants per locus

Linkage disequilibrium

Combinations of alleles

ABC

Class-I

DRBDRADQB1DQA1DPB1DPA1

Class-II

Proteinvariants

Proteinvariants

390711210

4512

5725

11214

HLA-Antibodies

Pregnancy - Antigens from the father

Transfusion - leukocytes

Transplantation - HLA mismatches donor

Contra-indication for transplantation

Decreased chance finding suitable donor

Some patients have antibodies against >85% of potential donors

Current antibody status ~ non-current

Histocompatibility in Organ Transplantation

Purpose - prevention of rejection

Matching - HLA class-I: A and B (and C) antigens- HLA class-II: DR (and DQ) antigens- ABO

HLA-antibodies - sensitization- allo- vs autoantibodies- screening- cross-match

Hyperacute rejection of a renal allograft

monomer

most prevalent Ig in serum,

longenst halflife (23 days)

4 subklasses:

IgG1: 70%

IgG2: 20%

IgG3: 7%

IgG4: 3%

IgG

2 forms

1. Membrane bound monomer

= B cel antigen receptor

2. free as pentamer (a lot in the circulation)

> 10 binding sites!

produced during primairy immune response

IgM

IgMIgM & & IgGIgG antibodiesantibodies

Primary & secondary immune responsePrimary & secondary immune response

- specificity

biologicalactivitity

=effector function

Antibodies = multifunctional adaptors

- diversity

Hyperacute Rejection

Types of Humoral Rejection (I)

Occurs when the recipient has previously been sensitized to the donor tissue

Caused by complement fixation of pre-existing antibodies against thetransplanted tissue, causing damage and extensive necrosis

Rejection starts within minutes of reperfusion

Relatively rare now with routine crossmatching of donor/recipient serum

Acute Humoral Rejection

Chronic Humoral Rejection

Complement mediated Damage

IgG1, IgG3 and IgM

Types of Humoral Rejection (II)

Hyperacute Rejection

Characterized by the production of anti-class-I and –II antibodies against the donor tissue (C4D on PTC)

Rapid loss of graft function (days), any time after transplantation

Treatment involves IVIG, plasmapheresis and/or rituximab (=anti-CD20)

Acute Humoral Rejection

Chronic Humoral Rejection

C4D staining of peritubular capillaries

Positive Negative

Types of Humoral Rejection (III)

Hyperacute Rejection

Transplant glomerulopathy is strongly associated with circulating antibodies to donor HLA class-II antigens and a poor prognosis

The "ABCD tetrad: The combination of alloantibody, basement membrane multilamination, C4d, and duplication of the GBM

Outcome and optimal therapy not yet defined

Acute Humoral Rejection

Chronic Humoral Rejection

Stages of Humoral Alloreactivity

Crossmatch & HLA antibody screening

Patient serumT-cells: class-IB-cells: class-II Complement Interpretation

Limitations of CDC

Cells have more than 1 type of HLA-antigen on their surface

Literature: positive class-I crossmatches (T-cells) are o.k.50-75% positive class-II crossmatches (B cells) are incorrect!

Interpretation heavily depends on quality of the cells

A1, A2, B7, B8

Positive

A23, A24, B13, B15

Negative

A1, A24, B13, B15

A1, A2, B13, B15

A1, A2, B7, B15

Patient sera usually contain more than 1 HLA-specificity

Luminex

Antibody Screening by Luminex

Single HLA-antigen Beads

MF

I

Sensitivity of HLA Antibody Assays

100,000 1000

LuminexBeads withsoluble HLAantigens

FACSXmatch Tor B cells

Microarray/ELISAWith solubleHLA antigens

AHG-CDCT cellXmatch

CDCT or B cellXmatch

ComplementEnzymeImmunofluorescence

Limits of detection: molecules of antibody