Methods of Increasing Graft Survival

Slide 1 · Methods of Increasing

Graft Survival

Allograft compatibility · immunosuppression · immune complications

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning objectives

Explain why HLA matching has different priorities across solid organs.

Trace the pharmacologic interruption of T-cell activation and proliferation.

Match major rejection mechanisms to the interventions.

Explain infection, malignancy, and tolerance as limits of graft survival.

Slide 3 · A graft survives through several protective layers

Protection is a combined immunologic and clinical strategy.

Before implantation

Reduce donor–recipient incompatibility.

Avoid preformed antibody reactions.

After implantation

Suppress T-cell activation and clonal expansion.

Address antibody-mediated injury.

Over time

Prevent progressive immune injury.

Balance immune suppression against infections and cancers.

Slide 4 · Allografts create an alloimmune problem

Allografts are transplanted between genetically different members of one species.

Recipient lymphocytes can recognize graft antigens as foreign.

T lymphocytes and antibodies can each mediate rejection.

Graft-survival strategies must account for both cellular and humoral immunity.

Slide 5 · HLA polymorphism creates donor–recipient disparity

The principal antigenic differences provoking allograft rejection involve HLA alleles.

Highly polymorphic HLA genes

Donor HLA differs from recipient

Host recognizes alloantigens

T-cell and B-cell responses

Genetic identity is exceptional: Identical twins are the special case.

HLA matching decreases disparities but does not replace other protective strategies.

Slide 6 · HLA matching: Kidney versus other major organs

Kidney transplantation

Matching important HLA alleles provides substantial benefit.

HLA-A, HLA-B, and HLA-DR.

Both alleles at each named locus matter.

Liver, heart, and lung

HLA matching as usually not performed.

Anatomic compatibility may dominate.

Clinical urgency and storage time also influence organ selection.

Slide 7 · Kidney allocation: The HLA loci emphasized

HLA-A and HLA-B are class I HLA loci.

HLA-DR is a class II HLA locus.

Matching of both alleles of HLA-A, -B, and -DR as particularly useful.

Improved compatibility reduces important alloantigenic differences encountered by the host.

Slide 8 · What “both alleles” means at the named HLA loci

Locus

Alleles considered

Teaching implication

HLA-A

Two donor / two recipient alleles

Assess differences across both alleles.

HLA-B

Two donor / two recipient alleles

A single matching allele does not mean a fully matched locus.

HLA-DR

Two donor / two recipient alleles

Class II disparity is relevant to T-cell responses.

Locus-level matching and overall genetic identity are not interchangeable.

Slide 9 · Why better HLA matching can protect a kidney graft

Fewer mismatched HLA determinants

Less alloimmune recognition

Reduced destructive immune response

Improved graft-survival potential

The causal interpretation follows the recognized role of HLA alloantigens in graft rejection.

HLA matching is beneficial but not a guarantee against rejection.

Slide 10 · Donor selection involves competing priorities

Immunologic compatibility

Donor–recipient HLA differences can drive rejection.

A closer match is beneficial for kidney transplantation.

Organ and recipient realities

Anatomical suitability must be considered.

Severe recipient illness can make timing decisive.

Time in storage is also a constraint.

The relative weight of HLA matching is organ-dependent.

Slide 11 · Application: Why the best HLA match may not be selected

A critically ill heart-transplant candidate needs a suitable donor urgently. A more closely HLA-matched organ may involve substantial delay.

Which priorities does the textbook describe as potentially overriding HLA matching?

Anatomic compatibility and severity of the underlying illness.

The need to minimize organ storage time.

Slide 12 · Preventing hyperacute rejection requires antibody awareness

Hyperacute rejection is mediated by antibodies already present before implantation.

These antibodies recognize graft endothelial antigens.

Relevant antibody targets include blood group antigens and donor HLA molecules.

Matching and antibody testing address a danger not prevented by delaying T-cell responses alone.

Slide 13 · Why a recipient may already possess anti-HLA antibodies

Prior exposure

Immunologic consequence

Previous transplantation

Recipient may have encountered nonself HLA antigens.

Blood transfusion

Exposure to allogeneic cells can induce anti-HLA antibodies.

Pregnancy

Exposure to fetal alloantigens can sensitize the recipient.

These are sensitization mechanisms, not a claim that every exposure causes antibodies.

Slide 14 · Crossmatching blocks the preformed-antibody pathway

Prospective donor identified

Recipient antibody status assessed

Donor-cell crossmatch performed

High-risk incompatibility avoided

ABO matching and donor-cell crossmatching to the rarity of hyperacute rejection.

Crossmatching and later immunosuppression address different phases of alloimmunity.

Slide 15 · Hyperacute rejection is an endothelial catastrophe

Preformed antibody binds graft

Complement activation

Endothelial damage + thrombosis

Ischemic necrosis

Because antibodies exist beforehand, injury can begin once perfusion is restored.

This mechanism explains the high priority of preventing incompatible transplantation.

Slide 16 · Selection measures cannot substitute for immunosuppression

Before graft implantation

Choose compatible donor and recipient where feasible.

Match blood group and assess donor-reactive antibodies.

Consider HLA matching in the organ-specific context.

After graft implantation

Alloreactive lymphocytes can still activate.

T-cell responses may damage parenchyma and vessels.

Except with identical twins, immunosuppressive therapy is necessary.

Slide 17 · Rejection mechanisms determine treatment targets

Pattern

Principal mechanism

Implication

Hyperacute

Preformed antibody → complement → thrombosis

Prevent incompatibility before implantation.

Acute cellular

Alloreactive T cells injure parenchyma/vessels

Reduce T-cell activation and responses.

Acute antibody-mediated

Antibody-dependent endothelial injury

Address the antibody-mediated component.

Chronic

Persistent vascular injury and fibrosis

Acute-rejection therapies have limitations.

Slide 18 · Acute T-cell rejection is a central prevention target

Acute rejection may occur in days or weeks, or after later reduction of immunosuppression.

CD8+ cytotoxic T lymphocytes can directly injure graft cells.

CD4+ T lymphocytes can produce cytokines and recruit inflammatory cells.

Accordingly, many immunosuppressive strategies target T-cell activation.

Slide 19 · Direct recognition can activate recipient T cells

Donor graft APC

Donor HLA presented directly

Recipient alloreactive T cell

Effector response

The direct pathway is emphasized in the source as important in acute CTL-mediated rejection.

Blocking downstream activation can reduce the consequences of direct recognition.

Slide 20 · Indirect recognition broadens the allograft response

Host APC takes up graft antigen

Antigen processing

Presentation to host T cell

Alloimmune activation

The indirect pathway particularly with chronic rejection.

Compatibility strategies reduce the antigenic differences driving both pathways.

Slide 21 · The two effector arms of cellular rejection

CD8+ cytotoxic T cells

Recognize relevant graft targets.

Can directly kill graft parenchymal cells.

Produce cellular tissue injury.

CD4+ helper T cells

Respond to allogeneic antigen presentation.

Produce cytokines.

Promote recruitment of inflammatory cells and vascular injury.

Slide 22 · T-cell activation amplifies graft injury

Alloantigen recognition

T-cell activation

Effector lymphocytes + cytokines

Tissue and vessel injury

Immunosuppressive drugs intervene before or during amplification of these responses.

The pathway clarifies why multiple pharmacologic targets can be complementary.

Slide 23 · Tubulitis reflects cellular attack on kidney tubules

Acute cellular rejection may show interstitial inflammatory infiltrates.

Lymphocytes may accumulate among tubular epithelial cells: Tubulitis.

Focal tubular epithelial injury may accompany the inflammation.

The pathologic pattern is consistent with effector T-cell activity.

Slide 24 · Endotheliitis identifies vascular cellular rejection

Lymphocytes may enter the space beneath graft vascular endothelium.

Endothelial swelling and intimal arteritis can be present.

Severe vascular involvement may include injury and necrosis of vessel walls.

These findings link T-cell responses to loss of vascular integrity.

Slide 25 · Antibody-mediated rejection uses a distinct route

Alloantibody binds endothelium

Classical complement pathway

Inflammation of microvasculature

Graft dysfunction

Kidney lesions may include glomerulitis and peritubular capillaritis.

C4d deposition may indicate activation of complement by antibodies.

Slide 26 · Histopathology helps identify the dominant immune mechanism

Finding in kidney graft

Interpretation

Tubulitis + interstitial inflammation

Typical acute T-cell–mediated rejection pattern.

Endotheliitis / intimal arteritis

Vascular pattern of cellular rejection.

Glomerular / peritubular capillaritis

Typical microvascular inflammation of antibody-mediated rejection.

C4d deposition

Evidence of complement activation in antibody-mediated injury.

Slide 27 · Immunosuppression is ordinarily indispensable

All donor–recipient combinations except identical twins require immunosuppressive treatment.

Even a carefully selected graft can provoke immune recognition.

Immunosuppressants limit rejection but impair protective immune responses.

The benefit must therefore be considered alongside treatment-associated infection and cancer risk.

Slide 28 · Immunosuppressive drugs act at different steps

The named drug classes suppress distinct functional components of alloimmunity.

Inflammation

Steroids reduce inflammatory responses.

They do not eliminate pre-existing HLA differences.

Cell expansion

Mycophenolate mofetil inhibits lymphocyte proliferation.

This curtails amplification after activation.

Activation signaling

Tacrolimus and cyclosporine inhibit calcineurin.

Reduced NFAT activation limits T-cell cytokine production.

Slide 29 · Corticosteroids reduce inflammatory injury

Steroids are listed among drugs routinely used for immunosuppression.

Their principal mechanism emphasized here is reduction of inflammation.

Inflammation is an important downstream consequence of alloreactive T-cell activation.

Steroid action is conceptually downstream of donor antigen recognition.

Slide 30 · Mycophenolate restrains lymphocyte proliferation

Alloantigen recognition

Lymphocyte activation

Clonal proliferation

Expanded immune attack

Mycophenolate mofetil acts on the lymphocyte-proliferation step.

The source does not assign it a role in correcting donor HLA mismatch.

Slide 31 · Calcineurin inhibitors suppress T-cell responses

Tacrolimus (FK506) and cyclosporine are both calcineurin inhibitors.

Calcineurin is a phosphatase required for activation of NFAT.

NFAT promotes transcription of several cytokine genes.

Inhibition reduces the T-cell signaling needed to mount an antigraft response.

Slide 32 · Calcineurin–NFAT links signaling to cytokine genes

T-cell activation signals

Calcineurin phosphatase

NFAT transcription factor

Cytokine gene transcription

IL-2 as an especially important NFAT-regulated cytokine.

Inhibiting calcineurin interrupts this sequence before cytokine transcription.

Slide 33 · Tacrolimus interrupts NFAT-dependent activation

Pharmacologic inhibition is applied to a specific signaling node.

Tacrolimus / cyclosporine

Calcineurin inhibited

NFAT activation reduced

T-cell cytokine response reduced

The drug action is upstream of the NFAT-driven cytokine program.

This explains suppression of cellular rejection without altering donor HLA identity.

Slide 34 · IL-2 is a key growth signal in the T-cell response

IL-2 as a growth factor encoded by an NFAT-responsive gene.

T-cell activation normally induces cytokine gene transcription.

Calcineurin inhibitors reduce the signaling leading to IL-2 transcription.

This mechanistic connection explains why calcineurin inhibition constrains T-cell responses.

Slide 35 · Steroids, mycophenolate and tacrolimus: Target map

Intervention

Textbook target or effect

Position in response

Steroids

Reduce inflammation

Inflammatory effector phase

Mycophenolate mofetil

Inhibits lymphocyte proliferation

Expansion of immune clones

Tacrolimus

Inhibits calcineurin → NFAT

Activation / cytokine transcription

Cyclosporine

Calcineurin inhibition

Activation / cytokine transcription

Slide 36 · A drug mechanism is not a rejection diagnosis

Medication mechanism

Blocks a signaling step or inflammatory consequence.

May broadly suppress protective host immunity.

Does not identify which lesion is present.

Rejection pathogenesis

Cellular injury reflects activated T cells.

Humoral injury reflects antibodies and complement.

Pathology distinguishes relevant tissue patterns.

Treatment reasoning starts from mechanism, not from drug names alone.

Slide 37 · T-cell activation requires costimulatory signaling

Graft alloantigen presented

B7 molecule on APC

CD28 receptor on T cell

Productive T-cell activation

B7 on graft-donor dendritic cells and CD28 on host T cells.

Interrupting this interaction can decrease the antigraft response early in sensitization.

Slide 38 · B7–CD28 costimulation: The interacting partners

Antigen-presenting cell

A dendritic cell can present graft alloantigen.

Its B7 molecules deliver a costimulatory signal.

Host T lymphocyte

Receives an antigen-recognition signal.

CD28 provides the receptor for B7 costimulation.

This is a cell–cell signaling interaction, not an antibody crossmatch.

Slide 39 · Blocking B7 interrupts early T-cell sensitization

B7-binding blocking protein

B7 costimulator unavailable

B7–CD28 interaction prevented

Reduced T-cell activation

The text describes administration of proteins that bind and block B7.

This targets costimulation rather than calcineurin signaling.

Slide 40 · Two distinct interventions in T-cell activation

Feature

Calcineurin inhibition

Costimulation blockade

Target

Intracellular calcineurin

B7 costimulatory molecules

Key consequence

Reduced NFAT-mediated transcription

Interrupts B7–CD28 signaling

Functional position

After T-cell triggering

Early sensitization / activation

Clinical purpose

Suppress alloreactive T-cell responses

Reduce antigraft T-cell activation

Slide 41 · Therapies for established rejection extend beyond maintenance drugs

T-cell–depleting antibodies among additional rejection treatments.

Pooled intravenous immunoglobulin (IVIG) is another named approach.

Plasmapheresis is used for severe antibody-mediated rejection.

Mechanism-directed assessment distinguishes cellular from antibody-mediated injury.

Slide 42 · T-cell–depleting antibodies reduce effector-cell availability

Alloreactive T-cell population

T-cell–depleting antibody therapy

Reduced T-cell availability

Reduced cellular immune attack

This as a treatment used for graft rejection.

The supplied text does not define antibody products, doses, or specific treatment algorithms.

Slide 43 · IVIG is mentioned with mechanistic uncertainty

Pooled intravenous IgG is listed as a therapy used to treat rejection.

Suppression of inflammation as an effect of IVIG.

The textbook explicitly states that the mechanisms are unknown.

A proposed detailed pathway should not be presented as established from this excerpt.

Slide 44 · Plasmapheresis targets severe antibody-mediated rejection

Antibody-mediated vascular injury

Severe clinical rejection

Plasmapheresis used

Antibody-directed intervention

The textbook places plasmapheresis specifically in severe antibody-mediated rejection.

No efficacy percentages, procedural details, or dosing schedules are provided.

Slide 45 · Selecting a mechanistic response to graft injury

Observed problem

Immune axis emphasized

Interventions discussed

Active cellular rejection

Recipient T-cell responses

T-cell immunosuppression; T-cell–depleting antibodies

Antibody-mediated rejection

Antibody + complement / endothelium

IVIG; Plasmapheresis in severe cases

Hyperacute antibody reaction

Preformed circulating antibody

Prevent through matching and crossmatch

Chronic progressive rejection

Vascular remodeling / fibrosis

Most acute-rejection therapies remain inadequate

Slide 46 · Chronic rejection progresses through vascular remodeling

Alloreactive T cells / antibodies

Persistent graft inflammation

Intimal smooth-muscle growth

Vessel narrowing + graft loss

T-cell cytokines can stimulate smooth-muscle cells and fibroblasts.

Chronic damage is more refractory to available therapies than acute rejection.

Slide 47 · Fibrosis links chronic immune injury to graft decline

Progressive vascular narrowing reduces long-term graft function.

Interstitial fibrosis and tubular atrophy may follow vascular injury in kidney grafts.

Transplant glomerulopathy can include duplicated capillary basement membranes.

These structural changes explain why preventing acute rejection does not abolish late graft loss.

Slide 48 · Acute success is not equivalent to lifelong graft survival

Improved short-term control

Therapy reduces many acute T-cell rejection episodes.

Effective suppression helps improve early graft survival.

Long-term vulnerability

Chronic vascular damage and fibrosis can continue.

Chronic rejection is refractory to most therapies.

Complications of immunosuppression accumulate.

A functioning graft is only one dimension of transplant success.

Slide 49 · Immunosuppression carries major biologic costs

Suppressing antigraft immunity also weakens protective host responses.

Opportunistic infections and cancers as major barriers.

These complications affect disease-free survival after transplantation.

More immune suppression is not a risk-free means of prolonging graft function.

Central trade-off: Prevent rejection while preserving protective immunity.

Slide 50 · Infection vulnerability spans multiple pathogen classes

Microbial class

Clinical implication

Bacterial

Increased susceptibility with immunosuppression.

Viral

Potential new infection or reactivation of latent viruses.

Fungal

Opportunistic infection risk in the immunosuppressed host.

Slide 51 · BK polyomavirus illustrates latent viral reactivation

Latent infection in urinary epithelium

Transplant immunosuppression

Viral reactivation

Renal tubular infection

The source highlights BK virus as a particularly important kidney-transplant complication.

Reactivation can threaten allograft function.

Slide 52 · BK polyomavirus can itself cause graft failure

BK virus persists latently in lower genitourinary epithelial cells of healthy persons.

Under immunosuppression, it may reactivate and involve renal tubules.

Renal infection can damage a transplanted kidney and impair function.

Graft dysfunction therefore does not automatically establish acute immune rejection.

Slide 53 · Graft dysfunction: Rejection and infection are distinct

Immune rejection

Recipient anti-graft T cells or antibodies drive tissue injury.

Suppressing this immune response protects the graft.

BK virus–associated injury

Latent virus reactivates under immunosuppression.

Tubular infection can impair graft function.

Additional suppression cannot be assumed harmless.

The same treatment that protects against rejection can increase infection risk.

Slide 54 · Malignancy risks follow sustained immune suppression

Several cancers among transplant recipients.

Skin cancer

Overall skin-cancer risk is increased.

A clinically important long-term complication.

EBV-associated lymphoma

EBV-related lymphoid malignancy risk rises.

Latent oncogenic viral reactivation may contribute.

HPV-associated carcinoma

HPV-related squamous cell carcinoma is described.

Oncogenic viral reactivation is implicated.

Slide 55 · EBV-related lymphoma links immune control to cancer risk

Latent EBV persists

Host immunity suppressed

Viral control diminished

EBV-induced lymphomas may develop

This is a mechanistic teaching schematic consistent with the source’s stated association.

No incidence, risk ratio, screening protocol, or diagnostic criterion is asserted.

Slide 56 · HPV-associated carcinoma is another oncogenic-virus risk

Latent / persistent HPV

Immunosuppression

Reduced viral immune control

Squamous-cell carcinoma risk

HPV-induced squamous cell carcinomas among transplant-associated malignancies.

The exact cancer site and risk estimates are not specified in the excerpt.

Slide 57 · The goal is disease-free survival, not only graft function

Successful transplantation aims to preserve a functioning graft.

Opportunistic infection can cause serious morbidity.

Skin cancers and virus-associated malignancies may compromise long-term outcomes.

Graft survival should therefore be interpreted with recipient safety in mind.

Slide 58 · Donor-specific tolerance is the theoretical ideal

Immune system recognizes donor graft

Antigraft response selectively silenced

Antimicrobial immunity preserved

Graft protection without broad suppression

The source states that efforts to induce such tolerance have not yet succeeded.

The diagram describes the intended goal, not an achieved clinical pathway.

Slide 59 · Broad suppression differs from donor-specific tolerance

Conventional immunosuppression

Lowers immune responses to graft alloantigens.

Also diminishes defensive responses to microbes.

Creates infection and oncologic risks.

Desired donor-specific tolerance

Would selectively reduce antigraft reactivity.

Would preserve responses to pathogens.

Remains an unrealized goal in the cited text.

Slide 60 · Case reasoning: Early vascular graft injury

A renal allograft rapidly develops vascular thrombosis after perfusion. The recipient had prior exposure to allogeneic cells.

Which prevention step addresses the relevant mechanism?

Assess preformed donor-reactive antibodies before transplantation.

ABO compatibility and donor-cell crossmatching reduce the risk of hyperacute rejection.

Slide 61 · Case reasoning: Later decline after immunosuppression change

A transplant recipient develops abrupt loss of graft function after immune-suppressing treatment is reduced.

Which pathophysiologic process should the clinician consider?

Acute rejection can occur late when immunosuppression is tapered or stopped.

Cellular and antibody-mediated patterns need mechanistic distinction.

Slide 62 · Case reasoning: Deteriorating kidney graft with viral risk

A kidney-transplant recipient receiving sustained immunosuppression develops impaired allograft function.

Why is immune rejection not the only explanation?

BK polyomavirus can reactivate during immunosuppression.

Renal tubular infection may itself cause graft failure.

Slide 63 · Integrated methods of improving graft survival

Stage / aim

Protective strategy

Main limitation

Organ selection

HLA matching where beneficial; Anatomic / urgency / storage considerations

Priorities vary by organ.

Avoid immediate loss

ABO compatibility; Donor antibody crossmatch

Does not eliminate later alloimmunity.

Prevent cellular rejection

Steroids, mycophenolate, calcineurin inhibitors, B7 blockade

General immune suppression carries risks.

Treat established rejection

T-cell depleting antibodies; IVIG; Plasmapheresis for severe AMR

Chronic injury remains difficult to reverse.

Future selectivity

Donor-specific immune tolerance

Not yet successful in textbook account.

Slide 64 · Consolidated mechanistic principles

HLA disparities are central alloantigens; Donor selection reduces but rarely removes this difference.

Calcineurin–NFAT–IL-2 signaling and B7–CD28 costimulation provide distinct T-cell targets.

Antibodies, complement, and graft endothelium require separate mechanistic attention.

Infection, malignancy, and chronic rejection limit the benefit of even effective acute immunosuppression.

Slide 65 · Integrated discussion: What should an effective strategy balance?

A donor organ is suitable, preformed-antibody incompatibility has been excluded, and a lifelong need to maintain the graft remains.

Which four considerations should frame the discussion?

Organ-specific matching and donor suitability; Control of alloreactive T cells.

Recognition of antibody-mediated injury; Protection against infection and malignancy.

Slide 66 · Primary textbook and source scope

Robbins, Cotran & Kumar. Pathologic Basis of Disease. 11th ed. Chapter 6: Diseases of the Immune System.

Primary assigned heading: “Methods of Increasing Graft Survival,” printed pages 210–211.

Mechanistic parent context: “Rejection of Tissue Transplants” and “Patterns and Mechanisms of Graft Rejection,” printed pages 208–210.

No external prescribing guidelines or nontextbook treatment outcomes are incorporated into this lecture.