5=TOLERANCE & TRANSPLANTATION

Learning Objectives ◼ Review central and peripheral developmental tolerance of lymphocytes that we explored earlier this semester ◼ Describe the role of immune privileged sites and T regs in tolerances ◼ Define the obstacles in organ transplantation and how we induce tolerance

TOLERANCE IS FAVORED WHEN: (3 L)

• LONG BLANK 

• LACK BLANK 

• LOW BLANK 

• LONG TERM PERSISTENCE OF ANTIGEN

• LACK OF ADJUVANT

• LOW LEVELS OF CO-STIMULATION

IMMUNOGEN OR TOLEROGEN TABLE WRITE OUT

IMMUNOGEN OR TOLEROGEN

PHYSICAL FORM OF ANTIGEN, ROUTE OF INJECTION, DOSE OF ANTIGEN ARE ALL EXAMPLES OF BLANK 

FACTORS WHICH AFFECT RESPONSE

IMMUNOGEN OR TOLEROGEN

• LARGE, AGGREGATED, COMPLEX MOLECULES, PROPERLY PROCESSED

• SUBCUTANEOUS OR INTRAMUSCULAR 

• OPTIMAL DOSE 

ARE ALL EXAMPLES OF BLANK 

WHAT FAVOR IMMUNE RESPONSE 

IMMUNOGEN OR TOLEROGEN

• SOLUBLE, AGGREGATE-FREE, SIMPLE SMALL MOLECULES, NOT PROCESSED

• ORAL OR SOMETIMES INTRAVENOUS 

• VERY LARGE OR VERY SMALL DOSE

ARE ALL EXAMPLES OF BLANK 

THOSE THAT FAVOR TOLERANCE

BLANK=PREVENTION OF AN IMMUNE RESPONSE AGAINST SELF STRUCTURES. MANY LAYERS OF THIS!

TOLERANCE (SELF TOLERANCE)

BLANK TOLERANCE-DELETION OF LYMPHOCYTES WITH RECEPTORS THAT RECOGNIZE SELF ANTIGENS BEFORE THEY MATURE DURING LYMPHOCYTE DEVELOPMENT

CENTRAL TOLERANCE

BLANK: REMOVE HIGH-AFFINITY TCRS AND BCRS THAT RECOGNIZE SELF-ANTIGEN 

NEGATIVE SELECTION 

WHAT ARE THE 3 RESULTS OF CENTRAL TOLERANCE IN B CELLS?

• NON-SELF REACTIVE B CELL

• DELETION

• ANERGC B CELKL

FOR CENTRAL TOLERANCE: NEGATIVE SELECTION OF B CELLS…

REMOVE OR EDIT BCRS THAT BIND TO ANTIGEN

FOR CENTRAL TOLERANCE: T CELLS THYMIC SELECTION (LIST THE 2 BULLETS)

• AFFINITY MODEL 

• USE OF MTEC AND AIRE+ CTECS 

WHAT IS THE MAIN ISSUE WITH CENTRAL TOLERANCE? 

“LEAKY” TOLERANCE MAY NOT ELIMINATE ALL SELF-REACTIVE CELLS 

WHAT ARE THE REASONS “LEAKY” TOLERANCE TO SELF-REACTIVE CELLS HAPPENS? (HINT 4) 

• Not all self-antigens are expressed in central lymphoid organs: Tissue-Restricted Antigens

• Weakly reactive cells may not be eliminated

• Aging affects the thymic environment and this may impair proper negative selection

• Genetic defects that impact apoptosis pathways or regulatory pathways

“LEAKY” CENTRAL TOLERANCE 

BLANK AFFECTS THE THYMIC ENVIRONMENT—> IMPAIR PROPER NEGATIVE SELECTION 

AGING

“LEAKY” CENTRAL TOLERANCE 

GENETIC DEFECTS CAN IMPACT WHAT TWO PATHWAYS 

APOPTOSIS OR REGULATORY PATHWAYS

WHAT ARE TISSUE-RESTRICTED ANTIGENS?

NOT ALL SELF-ANTIGENS ARE EXPRESSED IN CENTRAL LYMPHOID ORGANS

BLANK TOLERANCE: RENDERS SELF-REACTIVE LYMPHOCYTES NONRESPOSIVENESS OR ACTIVELY GENERATES INHIBITING LYMPHOCYTES (T-REGS)

PERIPHERAL TOLERANCE

FOR PERIPHERAL TOLERANCE,

BLANK CAN ALSO ARISE FROM A LACK OF COSTIMULATION SIGNAL FROM APC 

TREGS 

PERIPHERAL TOLERANCE

COMPARED TO TREGS, BLANK OFTEN LACK THESE COSTIMULATION SIGNALS FROM APC 

TOLEROGENIC DCS 

WHAT IS CLONAL SELECTION?

ACTIVATION AND DIFFERENTIATION OF EFFECTOR T CELLS THAT RECOGNIZE FOREIGN ANTIGEN

WHAT IS PERIPHERAL TOLERANCE?

DELETION, ANERGY, OR INDUCTION OF REGULATORY FUNCTION IN T CELLS RECOGNIZING SELF ANTIGEN

MATCH WHETHER PERIPHERAL TOLERANCE VS. CLONAL SELECTION

BLANK: ACTIVATION AND DIFFERENTIATION OF EFFECTOR T CELLS THAT RECOGNIZE FOREIGN ANTIGEN 

BLANK: DELETION, ANERGY, OR INDUCTION OF REGULATORY FUNCTION IN T CELLS RECOGNIZING SELF ANTIGEN 

CLONAL SELECTION: ACTIVATION AND DIFFERENTIATION OF EFFECTOR T CELLS THAT RECOGNIZE FOREIGN ANTIGEN 

PERIPHERAL TOLERANCE: DELETION, ANERGY, OR INDUCTION OF REGULATORY FUNCTION IN T CELLS RECOGNIZING SELF ANTIGEN 

THIS EXPERIMENT IN NOD (NON-OBESE DIABETIC) MICE IS CALLED WHAT 

• ADOPTIVE TRANSFER 

WHAT DOES NOD STAND FOR? 

NON-OBESE DIABETIC 

IN THIS DIAGRAM, WHAT DOES CY STAND FOR?

• CY=TRIGGER TO INDUCE AUTOIMMUNE DIABETES

THESE ARE ALL CHARACTERISTICS OF WHAT? 

• Diverse cell type with affinity to self antigen

• Defining molecules:

  • CD25+, CTLA-4, high levels of IL- 2R, and FoxP3 master transcription factor

  • Clinical significance: Mutation in FoxP3 (X-linked) cause multi-organ autoimmunity

• CD4+ T reg

  • Clinical significance: Without these cells, IBD in mice is common

• CD8+ T regs - recognize Ag/MHC and nonclassical lipids

TREGS

WHAT ARE THE 4 DEFINING MOLECULES OF TREGS?

• CD25+

• CTLA-4

• HIGH LEVELS OF IL-2R

• FOXP3 MASTER TRANSCRIPTION FACTOR

WHAT IS THE CLINICAL SIGNIFICANCE OF TREGS?

• MUTATION IN FOXP3 (X-LINKED) CAUSE MULTI-ORGAN AUTOIMMUNITY

WHAT IS THE CLINICAL SIGNIFICANCE OF CD4+ T REGS

• WITHOUT THEM, IBD IN MICE IS COMMON

WHAT RECOGNIZE AG/MHC AND NONCLASSICAL LIPIDS?

CD8+ T REGS

WHAT ARE THE 5 TREG FUNCTIONS? (IHCMD)

1. Inhibitory cytokines (IL-10 & TGF−BETA)

2. High affinity IL-2R sequesters IL-2

3. Cytolysis: Perforin, Granzyme, FasL

4. Metabolism changes → decrease T cell function

• Delivery cAMP via gap junctions

5. “Decommission” APCs. Block APCs that bind to same antigen. Engagement of CTLA-4

on Tregs causes the following:

• Decrease pro-inflammatory cytokines,

• Kynurenine production from tryptophan = immunoinhibitory microenvironment

•  Decrease surface expression of costimulatory molecules like CD80/86

• Decrease MHC class II expression

TREG FUNCTIONS:

BLANK PRODUCTION FROM TRYPTOPHAN = IMMUNOINHIBITORY MICROENVIRONMENT

TREG FUNCTIONS:

KYNURENINE PRODUCTION FROM TRYPTOPHAN = IMMUNOINHIBITORY MICROENVIRONMENT

TREG FUNCTIONS 

“DECOMMISSION” APCS. BLOCK APCS THAT BIND TO THE SAME ANTIGEN. ENGAGEMENT OF CTLA-4 ON TREGS CAUSES WHAT 4 THINGS? (DKDD)

• DECREASE PRO-INFLAMMATORY CYTOKINES

• KYNURENINE PRODUCTION FROM TRYTOPHAN=IMMUNOINHIBITORY MICROENVIRONMENT

• DECREASE SURFACE EXPRESSION OF COSTIMULATORY MOLECULES LIKE CD80/86

• DECREASE MHC CLASS II EXPRESSION

DRAW OUT TREG CELL AND DENDRITIC CELL

T REGS FUNCTION 

An interesting “BLANK” effect can occur

• A TREG that interacts with an APC can suppress T cells that engage with separate Ag-MHC class II complexes on the APC surface usually through down regulating APC costimulatory signals

T REGS FUNCTION 

An interesting “BYSTANDER SUPPRESSION” effect can occur

• A TREG that interacts with an APC can suppress T cells that engage with separate Ag-MHC class II complexes on the APC surface usually through down regulating APC costimulatory signals

TREGS CAN ARISE FROM WHAT TWO THINGS?

CENTRAL OR PERIPHERAL TOLERANCE

WHAT HAPPENS TO TREG WHEN “BYSTANDER SUPPRESSION” EFEFCT OCCURS?

A TREG that interacts with an APC can suppress T cells that engage with separate Ag-MHC class II complexes on the APC surface usually through down regulating APC costimulatory signals

HOW DOES A TREG (THAT INTERACTS WITH AN APC) SUPPRESS T CELLS THAT ENGAGE WITH SEPARATE AG-MHC CLASS II COMPLEXES ON THE APC SURFACE? 

• BY DOWN REGULATING APC COSTIMULATORY SIGNALS 

  

WHAT ARE REGULATORY CD8+ T CELLS (HINT: 3 BULLETS)

Complex, heterogenous cell population that is still under investigation

• Appear after binding to self Ag-MHC class in the presence of TGF-β cytokine

• Deficient mice = colitis (lack of tolerance to commensal

microbes?)

WHAT ARE COMPLEX, HETEROGENOUS CELL POPULATION THAT IS STILL UNDER INVESTIGATION? 

REGULATORY CD8+ T CELLS 

DEFICIENT MICE=

COLITIS (LACK OF TOLERANCE TO COMMENSAL MICROBES?)

WHEN DO REGULATORY CD8+ T CELLS APPEAR?

AFTER BINDING TO SELF AG-MHC CLASS IN THE PRESENCE OF TGF-BETA CYTOKINE

REGULATORY CD8+ T CELLS APPEAR AFTER BINDING TO SELF AG-MHC CLASS IN THE PRESENCE OF…

TGF-BETA CYTOKINE

HOW ARE CD8+ T REGS SIMILAR TO CD4+ T REGS MECHANISMS TO SUPPRESS ACTIVITY (4 WAYS) 

• KILL CD4+ T CELL WITH PERFORIN AND FASL 

• CYTOKINE SECRETION (IL-10 AND TGF-BETA) 

• INHIBITION AND LYSIS OF APCS

• REGULATION OF EFFECTOR CELLS THAT BIND THE SAME AG 

HOW DO CD4+ T REGS KILL CD4+ T CELLS?

WITH PERFORIN AND FASL

WHAT IS ANOTHER WAY TO SAY B REGULATORY CELLS

B10 CELLS

BLANK CELLS

• Newly characterized and a lot yet to learn

• Secrete IL-10, IL-35, TGf-BETA 

• They can present antigen in a tolerogenic fashion (low costimulatory molecule expression) → Treg formation

• Engagement with Th17 cells may downregulate their function

• PD-L1 and FasL expression on Bregs can suppress T cell activation or induce apoptosis

B REGULATORY CELLS (B10 CELLS) 

• Newly characterized and a lot yet to learn

• Secrete IL-10, IL-35, TGf-BETA 

• They can present antigen in a tolerogenic fashion (low costimulatory molecule expression) → Treg formation

• Engagement with Th17 cells may downregulate their function

• PD-L1 and FasL expression on Bregs can suppress T cell activation or induce apoptosis

WHAT CELLS MAY GET DOWNREGULATED AFTER ENGAGEMENT WITH TH17 CELLS?

• B REGULATORY CELLS (B 10 CELLS)

BLANK AND BLANK EXPRESSION ON BREGS CAN SUPPRESS T CELL ACTIVATION OR INDUCE APOPTOSIS 

PD-L1 AND FASL EXPRESSION ON BREGS CAN SUPPRESS T CELL ACTIVATION OR INDUCE APOPTOSIS 

HOW CAN B10 CELLS FORM TREGS?

• THEY CAN PRESENT ANTIGEN IN A TOLEROGENIC FASHION (LOW COSTIMULATORY MOLECULE EXPRESSION) 

WHAT 3 THINGS DO B10 CELLS SECRETE?

• IL-10

• IL-35

• TGF-BETA 

WHAT CELLS ARE NEWLY CHARACTERIZED AND A LOT TO LEARN

B REGULATORY CELLS (B10)

WHAT ARE MDSCS?

MYELOID DERIVED SUPPRESSOR CELLS

WHERE ARE MDSCS FOUND AND THIS LEADS TO WHAT?

AT TUMOR SITES—> POOR PROGNOSIS

HOW DO MDSCS REDUCE IMMUNE RESPONSE (HINT: 3 THINGS)

• INHIBITORY CYTOKINES 

• CHEMICALS

• IMMUNOSUPPRESSIVE CELL RECEPTORS 

BLANK ARE IMMATURE HETEROGENOUS GROUP OF MYELOID CELLS (GRANULOCYTES AND MONOCYTES) THAT ARRIVE AT SITES OF INFECTION, INFLAMMATION, OR TUMORS 

MYELOID DERIVED SUPPRESSOR CELLS (MDSCS) ARE IMMATURE HETEROGENOUS GROUP OF MYELOID CELLS (GRANULOCYTES AND MONOCYTES) THAT ARRIVE AT SITES OF INFECTION, INFLAMMATION, OR TUMORS 

MDSCS ARRIVE AT WHAT THREE SITES?

INFECTION, INFLAMMATION, TUMORS

JUST FOR REFERENCE: MYELOID DERIVED SUPPRESSOR CELLS: MECHANISMS OF IMMUNE INHIBITION, WHAT IS THIS DIAGRAM SHOWING? 

WOW, SO MANY WAYS TO BLOCK IMMUNE SURVEILLANCE! 

TOLERANCE

BLANK-TISSUE THAT IS PROTECTED FROM IMMUNE ATTACK 

TOLERANCE

IMMUNE PRIVILEGED SITES-TISSUE THAT IS PROTECTED FROM IMMUNE ATTACK 

WHAT ARE IMMUNE PRIVILEGED SITES?

TISSUE THAT IS PROTECTED FROM IMMUNE ATTACK

What are the 3 major things in tolerace? 

• antigen sequestration 

• restricted immune entry 

• limited immune cells present 

tolerance

what is antigen sequestration?

• Lack of lymphatic drainage (anterior and lens of eye)

• Ags are isolated from interaction with immune cells

tolerance

what is restricted immune entry? 

blood-brain barrier

tolerance

what is limited immune cells present? 

few immune cells (cornea) 

in tolerance, damage to such areas may expose their blank to immune responses, initiating blank 

antigen, damage potential 

Immune tolerance in pregnancy

blank 

• Separate fetal and maternal blood systems

• T regs present

• Present only certain MHC I isotypes to avoid T cell and NK cell activation

• Syncytium – fused placental cells so no immune cells or maternal blood can migrate through

• Special uterine and fetal glycoproteins suppress immune response

Immune tolerance in pregnancy

Placenta-immunological barrier  

• Separate fetal and maternal blood systems

• T regs present

• Present only certain MHC I isotypes to avoid T cell and NK cell activation

• Syncytium – fused placental cells so no immune cells or maternal blood can migrate through

• Special uterine and fetal glycoproteins suppress immune response

during pregnancy, more at risk for blank

during pregnancy, more at risk for infections!

immune tolerance in pregancy:

placentra-immunological barrier (list the 5 characteristics) 

• Separate fetal and maternal blood systems

• T regs present

• Present only certain MHC I isotypes to avoid T cell and NK cell activation

• Syncytium – fused placental cells so no immune cells or maternal blood can migrate through

• Special uterine and fetal glycoproteins suppress immune response

the placenta presents what to avoid t cell and nk cell activation?

only certain MHC I isotypes

immune tolerance in pregnancy, what suppress immune response?

special uterine and fetal glycoproteins

blank-fused placental cells so no immune cells or maternal blood can migrate through

syncytium-fused placental cells so no immune cells or maternal blood can migrate through

immune tolerance in pregnancy

placenta-immunological barrier 

what is syncytium? 

fused placental cells so no immune cells or maternal blood can migrate through 

what induces tolerance?

transplantation

what are the current goals of transplantation?

minimize graft rejection

• demand is high 

• availability of genetically identical donors is low 

minimize rejection without suppressing entire immune response

for timeline of transplantation:

blank pioneered kidney transplantation and conducted the first non-twin living kidney transplant in 1960 and develop a perfusion instrument to preserve kidneys for up to 50 hours.

dr samuel kountz

dr samuel kountz (4 facts) 

• pioneered kidney transplantation

• conducted first non-twin living kidney transplant 

• in 1960 

• develop a perfusion instrument to preserve kidneys for up to 50 hours

Who were the two doctors mentioned in regards to organ transplantations?

• Dr Samuel Kountz

• Dr Velma Scantlebury-White

transplantation immunology

how many corneal tissue grafts (2016) 

46,000!

Transplantation terminology

• blank = self tissue grafted to another self area (skin grafts, blood vessels for bypass heart surgery)

• blank = transplant between genetically identical individuals (inbred strains of mice, identical twins)

• blank = tissue transferred between genetically different members of the same species (majority of transplant cases)

• blank = tissue transferred between different species (baboon heart into a human)

• blank – tissue that share sufficient antigen similarity to decrease chance of rejection

Transplantation terminology

• Autograft = self tissue grafted to another self area (skin grafts, blood vessels for bypass heart surgery)

• Isograft = transplant between genetically identical individuals (inbred strains of mice, identical twins)

• Allograft = tissue transferred between genetically different members of the same species (majority of transplant cases)

• Xenograft = tissue transferred between different species (baboon heart into a human)

• Histocompatibility – tissue that share sufficient antigen similarity to decrease chance of rejection

transplantation terminology

what is an autograft? 

self tissue grafted to another self area

• skin grafts, blood vessels for bypass heart surgery

transplantation terminology

what is an isograft?

transplant between genetically identical individuals

(inbred strains of mice, identical twins)

transplantation terminology

what is an allograft?

 tissue transferred between genetically different members of the same species

(majority of transplant cases)

transplantation terminology

what is a xenograft? 

 tissue transferred between different species (baboon heart into a human)

transplantation terminology

what is histocompatibility? 

 tissue that share sufficient antigen similarity to decrease chance of rejection

List the xenotransplantation 4 facts with help

• blank slices of chimpanzee testes in humans (1920s) 

• chimpanzee kidney survived blank months in one human (1963-64), rejected in blank # of other humans

• blank animal liver survived 70 days in a human (1992)

• genetically modified blank animal body part worked for 57 hours in 2 brain-dead patients

List the xenotransplantation 4 facts with help

• “zest for life” slices of chimpanzee testes in humans (1920s) 

• chimpanzee kidney survived 9 months in one human (1963-64), rejected in 12 other humans

• baboon liver survived 70 days in a human (1992)

• genetically modified pig kidney  worked for 57 hours in 2 brain-dead patients 

Xenotransplantation

Why did they do “zest for life” slices of chimpanzee testes in humans in 1920s?

• to increase labido (sex drive)

• macrophages clean this up after infection happened—> stopped doing it! 

draw out the xenotransplantation model 

What are the 2 reasons they use pig transplants in humans?

• very fast to reproduce

• similar organ size as humans

  

What are the 3 issues with pig transplants?

• they have alpha-gal (sugar molecule) that we do not have 

• they lack complement inhibitors like DAF and protectin 

• Don’t know all their viruses

  

list the 4 facts about xenotransplantation (zcbg)

• “zest for life” slices of chimpanzee testes in humans (1920s) 

• chimpanzee kidney survived 9 months in one human (1963-64), rejected in 12 other humans

• baboon liver survived 70 days in a human (1992)

• genetically modified pig kidney  worked for 57 hours in 2 brain-dead patients 

New breakthroughs in transplantation

• face transplant (partial 2005, full 2010)

• whole face and eye transplant (2023)

  • then showed video with patient one year later 

From the video on new breakthroughs in transplantation what term did they use for transplant not rejected?

It was viable!

blank 

• “matching” 

1. Blood group Ag differences = most intense graft rejections. They are the first items to be matched between donor/recipient.

2. MHC compatibility is determined next. Siblings/parents are first choice due to better matches

3. Cross-Matching. A blood test that determines compatibility. Analyzes circulating Abs, especially to HLA

4. Anti-rejection drugs allow organ transplants between completely mismatched people

Transplant success

• “matching” 

1. Blood group Ag differences = most intense graft rejections. They are the first items to be matched between donor/recipient.

2. MHC compatibility is determined next. Siblings/parents are first choice due to better matches

3. Cross-Matching. A blood test that determines compatibility. Analyzes circulating Abs, especially to HLA

4. Anti-rejection drugs allow organ transplants between completely mismatched people

“matching” is part of what?

transplant success

what leads to the most intense graft rejections

blood group ag differences

what are the first items to be matched between donor/recipient

Blood group Ag differences

What does luminex bead-based screening assays look for?

• look for lack/no lack of antibody binding

  

what is determined after blood group Ag differences in transplant success

MHC compatibility

siblings/parents are first choice in what due to better matches

MHC compatibility

What is the blood test that determines compatibility. Analyzes circulating Abs, especially to HLA

Cross-matching Department: Pediatrics