Transplantation Immunology 231n6
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C.G,Vipin Shankar III Sem MSc. Biochemistry
Transplantation
Refers to the act of transferring cells, tissues or organs from one site to another.
The desire to accomplish transplants, stems from the realization that many diseases can be cured by implantation of a healthy organ, tissue or cells (a graft) from one individual (the donor), to another in need of the transplant (the recipient or the host).
History Indian mythology says, Lord Ganesha has a transplanted head, and He remains our favorite deity….
History…
Sushrutha samhita…
Sushruta gives s of skin transplantations done on wounded soldiers.
History…
Alexis Carrel (1908)…
First systematic study of transplantation. Interchanged both kidneys in a series of 9 cats. Survived up to 25 days. Established that tranplanted organ could carry out its normal function in a recipient.
History….
Medawar (1940s)…
Has given insights into nature of graft rejection while working with burn patients of World War II. Grafts of skin from one region of the body to another in the same patient was accepted easily, where as grafts obtained from close relatives were rejected. The intensity of a graft being rejected a second time was faster.
History…
Medawar…
Discovered that prior sensitization with donor cells led to increased rejection of a subsequent graft.
The Timeline of Transplantation
1906 -First corneal transplant by Austrian ophthalmologist Dr. Edward Zim.
1908 -First skin allograft by Swiss surgeon Jacques Louis Reverdin.
1908 -Successful first cadaver knee t transplant by Dr Eric Lexer.
1911 -Initial use of homologous vein tissue in arterial reconstruction.
1918 -First blood transfusion.
The Timeline of Transplantation….
1949 -Establishment of US Navy Tissue Bank.
1954 -First successful living-related kidney transplant from identical twins performed by Dr. Joseph Murray and Dr. David Hume in Boston, MA. The recipient had normal kidney function for eight years.
1955 -Initial fresh heart valve allograft put into descending aorta.
1955 -Frozen venous allograft for femoral artery by.
1962 -First fresh heart valves implanted into cardiac position.
The Timeline of Transplantation….
1962 -First successful cadaveric kidney transplant by Dr. Joseph Murray and Dr. David Hume in Boston, MA. The recipient had normal kidney function for 21 months.
1963 -First liver transplant performed by Dr. Thomas Starzl..
1963 -First lung transplant performed by Dr. James Hardy at the University of Mississippi Medical Center, Jackson, MS.
1967 -First heart transplant performed by Dr. Christian Bernard at Groate Shure Hospital, South Africa. The recipient had normal heart function for 19 months.
1967 - First successful pancreas transplant performed by Dr. Richard C. Lillehei at the University of Minnesota.
The Timeline of Transplantation….
1968 -Brain death criteria created.
1968 -The Uniform Anatomical Gift Act. Legislation allows gift of organs to others.
1971 -Frozen heart valves used in allograft.
1971 -Introduction of cryo-preserved human skin allografts.
1972 -The Uniform Anatomical Gift Act establishes the Uniform Organ Donor Card as a legal document in all 50 states making it possible for anyone 18 years or older to legally donate his or her organs upon death.
The Timeline of Transplantation….
1972 -End Stage Renal Disease Act paves way for Medicare coverage of all kidney transplants.
1974 -First use of cryo-preserved venous allograft.
1978 -Cyclosporin begins testing.
1979 -Living related pancreas transplanted, Minneapolis, MN.
1981 -Brain death criteria expanded by President's Commission for Study of Ethical Problems in Medicine and Biomedical Research.
The Timeline of Transplantation….
1981 -First heart and lung transplant performed by Dr. Norman Shumway at Stanford University Medical Center, Stanford, CA.
1982 -Barney Clark receives the first permanent artificial heart at the University of Utah.
1983 -FDA approval of cyclosporine, the most successful antirejection medication developed to date.
1984 -First heart / liver transplant performed by Dr. Starzl at the Children's Hospital of Pittsburgh.
1984 -Baby Fae receives a walnut-sized baboon heart in an operation at Loma Linda University Medical Center. She was the first infant to receive an animal organ. Baby Fae lived for 21 days.
The Timeline of Transplantation….
1984 -National Organ Transplant Act (Public Law 98.507) establishes nationwide computer registry operated by the United Network for Organ Sharing (UNOS). The Act also authorizes financial for organ procurement organizations and outlaws purchase or sale of organs.
1985 -New York State, Oregon, and Pennsylvania Required Request Law. Mandates all potential organ and tissue donors be approached for donation. Soon thereafter, all remaining 47 states follow suit.
1986 -Consolidated Omnibus Budget Reconciliation Act ed. Requires all potential donors to be approached, superseding state laws and adding hospitals must comply to receive Medicare benefits.
The Timeline of Transplantation….
1988 -FDA approval of Viaspan or UW solution, greatly extends preservation time for livers.
1988 -t Commission on Accreditation of Health Care Organizations sets donor identification and notification standards. Requires the hospitals to have policies and procedures in place for the identification, referral and procurement of organs and tissues.
1989 -Dr. Thomas Starzl at the University of Pittsburgh reports clinical success of promising new anti-rejection drug, FK-506.
1989 -First liver transplant from a living related donor.
The Timeline of Transplantation….
1990 -Lung transplantation attempted as cure for Cystic Fibrosis.
1990 -Dr. Joseph Murray (performed first kidney transplant) awarded Nobel Prize for Medicine.
1990 -Dr. Thomas (pioneered bone marrow transplants as a cure for leukemia) awarded Nobel Prize for Medicine.
1990 -First successful heart related lung transplant.
1991 -First attempt at partial lung transplant.
The Timeline of Transplantation….
1991 -First successful small intestine transplant.
1996 -U.S. surgeons at Barnes Hospital in St. Louis, University of California, San Francisco, and Stanford University Hospital perform split-liver transplants.
Classification of grafts
Autografts: Self-tissue transferred from one body site eo another in the same individual. Isografts: Tissue transferred between genetically identical individuals. Allograft / Homograft: Tissue transferred between genetically different of the same species. Xenograft / Heterograft: Tissue transferred between different species.
Autografts and allograftts are usually accepted, owing to the genetic identity between graft and host.
Because an allograft is genetically dissimilar to the host, it is often recognized as foreign by the immune system and is rejected.
Xenografts exhibit the greatest genetic disparity and therefore engender a vigorous graft rejection.
Allograft acceptance
Histocompatibility & Histoincompatibility. Antigens determining histocompatibility: coded by 40 different loci. Loci responsible for most vigorous rejection is the Major Histocompatibility Complex (MHC). ( H2 in mice and HLA in humans) MHC loci is closely linked and is inherited as a complete set (haplotype) from each parent.
Allograft rejection
Rate varies according to tissue involved. Skin grafts are rejected faster than kidney or heart transplants.
Mechanism of rejection
Avrion Mitchison (1950) : lymphocytes but not serum antibody can transfer allograft immunity. Rats devoid of thymus can even accept xenografts. T cells derived from allograft primed mouse transfer second set allograft rejection to an unprimed syngenic recipient. Long survival of allografts in children suffering from thymic defeciancy.
T lymphocytes are involved in graft rejection.
Both T cell sub populations CD4 and CD8 are involved in graft rejection. Studied by blocking either of the sub populations by monoclonal antibodies directed against them. Blocking CD8 alone : Graft rejected in 15 days. Blocking CD4 alone: Graft rejected in 15- 30 days. Blocking both: Graft survived up to 60 days.
Mechanism of graft rejection….
Primarily by cell mediated immune response to alloantigen (MHC antigen). Both delayed type hypersensitivity and cell mediated cytotoxicity reactions have been implicated. Two stages involved: a) Sensitization phase. b) Effector phase.
Sensitization phase
CD4 and CD8 T cells recognize alloantigens. Both major and minor histocompatibility complexes are recognized. Recognize both donor MHC and a peptide with in the cleft. Peptide in the cleft in case of MHC I is derived from protein synthesized by the allogenic cell. In case of MHC II, proteins taken up and processed by the endocyrtic path way of the allogenic APCs, are bound to the cleft.
Host TH is activated when it interacts with an APC expressing an antigen ligand – MHC complex and also provides a requisite co-stimulatory signal. Different cell populations, within the graft serve as APCs. Dendritic cells have high levels of MHC II and function as major APCs. APCs of host origin migrate into graft, endocytose the foreign antigen and present them as processed peptides with self MHCs.
enger leukocytes
A population of donor APCs migrating from the graft to the regional lymph nodes. Primarily dendritic cells with high levels of MHC II & normal levels of MHC I. Wide spread in mammalian tissues except brain. Express allogenic MHC Ag. Recognized as foreign. Stimulate immune activation of T lymphocytes in lymph nodes.
Other APCs include: a) Langerhans cells b) Endothelial cells lining the blood vessels. These express MHC I and MHC II.
Recognition of alloantigens induce vigorous T cell proliferation. Major proliferating cell is the CD 4 T cell which recognizes MHC II directly or alloantigen peptides presented by APCs.
Effector phase
Delayed type hyper sensitivity. CTL mediated cytotoxicity. Antibody – compliment lysis. Antibody dependent cell mediated cytotoxicity (ADCC).
Influx of T cells and macrophages. Promoted by cytokines produced by TDTH cells. Recognition of foreign class alloantigens on th graft by CD 8 cells lead to CTL mediated killing. CD 4 cells function as MHC II restricted cytotoxic cells responsible for graft rejection.
Cytokines released by TH cells play central role. (IL 2, IFN γ & TNF β) IL 2 promotes T cell proliferation. Necessary for generation of CTLs. IFN γ promotes development of DTH response, Promotes influx of macrophages and subsequent activation of macrophages into more destructive cells. TNF β has direct cytotoxic effect on graft cell, Induces expression of MHC I and IIon graft cell.
CD 40 in allograft rejection
Expressed on wide variety of cells including dendritic cells, B cells, macrophages and endothelial cells. Critical role in allograft rejection. Inhibition of CD 40 with mAbs prolongs rejection of cardiac allografts and renal allografts. Hypothesized that CD 40 has a role in sensitization phase of T cell.
Modes of rejection
Hyper acute rejection. Acute early rejection. Acute late rejection. Chronic rejection.
Hyper acute rejection
Occurs within minutes of transplantation. Characterized by micro thrombi in capillaries and sludging of blood cells. Caused by pre existing host serum Abs specific for Ag of graft. Ag- Ab complex activates compliment resulting in intense infiltration of neutrophills into the grafted tissue. Causes massive blood clot in capillaries preventing vascularization of grafts.
Presence of Ab against Ag of graft
Recipients of repeated blood transfusion. Repeated pregnancies. Previous grafts. Specific for blood group antigens.
Rejection of xenografts follow this mode.
Accelerated rejection
A subtype of hyper acute rejection. Ab produced immediately after tranaplants.
Acute early rejection
Rejection within 10 days or so. Severe infiltration of the grafts by mononuclear cells. Rupture of capillaries. Involves T cell mediated reactions.
Acute late rejection
Rejection from 11th day onwards, in patients istrated with immunosupressiue drugs. Deposition of Immunoglobulins in blood vessel walls. Induce platelet aggrgation in capillaries. ADCC occurs.
Chronic rejection
Develops months or years after transplantation. After acute reaction has subsided. Includes both humoral and cell mediated response.
Tissue typing
Identification of HLA in donor and recipient tissue. Donor and recipient screened for ABO blood group compatibility.
Microcytotoxicity
WBCs from donor and recipient taken in wells of a microtitre plate. Abs against various MHC I and II Ags are added. Incubated for some time. Compliment is then added. Cytotoxicity assessed by uptake of dye. Indicates presence or absence of MHC Ag.
Mixed lymphocyte reaction (MLR)
To quantify the degree of compatibility. X ray irradiated or mitomicin C treated donor lymphocytes mixed with recipient lymphocytes. Medium contains H3 Thymidine. Checked for proliferation of T cells. T cell proliferation measured by the amount of H3 Thymidineinto cell DNA. Greater the differentiation, more the amount of H3 Thymidine. Time consuming.
Immunosupressive therapy
Generalised immunosupression of responses to all antigens. Slows down proliferation of activated lymphocytes. 3 processses i. Surgical process. ii. Irradiation. iii. Drugs.
Surgical process
Thymectomy. Spleenectomy. Lymphadenectomy.
Total lymphoid irradiation (TLI)
Lymphocytes are extremely sensitive to radiation. Recipient receives multiple x- ray exposure to thymus, spleen and lymph nodes before transplantation. 200 rads/day for several days before transplantation. Total of 3400 rads. Bone marrow not irrradiated. Lymphoid stem cells proliferate and renew population of circulating lymphocytes. New lymphocytes are tolerant to Ag of the graft.
Drugs
Azathioprine (imuran): mitotic inhibitor. istrated just before transplantation. Diminishes T cell proliferation. Metabolised to 6-mercaptopurine which is converted to 6-mercaptopurine riboside. Structurally similar to inosinic acid, precursor of purine biosynthesis. Acts as a competitive inhibitor in purine biosynthesis. Both B and T cell proliferation is diminished.
6-mercaptopurine
6- mercapto purine riboside phosphate
Inosine monophosphate
Cyclophosphamide: . Alkylating agent. . Inserts into DNA forming cross links. . DNA disrupted. . Effective against rapidly dividing cells. . Given at the time of grafting. . Blocks T cell proliferation.
Corticosteriods
. Prednisone and Dexamethasone. . Anti inflammatory. . Exerts effects at various levels of immune response.
Cyclosporin A & Rapamycin . Fungal metabolites . Has immuno supressive properties. . Blocks activation of resting T cells. . Inhibits transcription of gene coding for IL2 receptor (IL2R).
Specific immunosupressive therapy
Monoclonal Antibodies directed against various molecules of immune system. Manipulation of CD40. Agents blocking co – stimulatory signals. Donor treatment with mAbs against T cells.
Transplants
Corneal transplants. Kidney transplants. Heart transplants Liver transplants. Bone marrow transplants. Skin transplants. Pancreas transplants.
References
Immunology; 5th edition; Richard.A.Goldsby, Thomas.J.Kindt, Barbara.A.Osborne, Janis Kuby. An introduction to immunology; C.V.Rao. www.whfreeman.com/immunology5e http://www.novartis-transplant.com/ http://en.wikipedia.org/wiki/Organ_transplant http://www.eurotransplant.nl/?id=timeline
Thank you……….
Transplantation
Refers to the act of transferring cells, tissues or organs from one site to another.
The desire to accomplish transplants, stems from the realization that many diseases can be cured by implantation of a healthy organ, tissue or cells (a graft) from one individual (the donor), to another in need of the transplant (the recipient or the host).
History Indian mythology says, Lord Ganesha has a transplanted head, and He remains our favorite deity….
History…
Sushrutha samhita…
Sushruta gives s of skin transplantations done on wounded soldiers.
History…
Alexis Carrel (1908)…
First systematic study of transplantation. Interchanged both kidneys in a series of 9 cats. Survived up to 25 days. Established that tranplanted organ could carry out its normal function in a recipient.
History….
Medawar (1940s)…
Has given insights into nature of graft rejection while working with burn patients of World War II. Grafts of skin from one region of the body to another in the same patient was accepted easily, where as grafts obtained from close relatives were rejected. The intensity of a graft being rejected a second time was faster.
History…
Medawar…
Discovered that prior sensitization with donor cells led to increased rejection of a subsequent graft.
The Timeline of Transplantation
1906 -First corneal transplant by Austrian ophthalmologist Dr. Edward Zim.
1908 -First skin allograft by Swiss surgeon Jacques Louis Reverdin.
1908 -Successful first cadaver knee t transplant by Dr Eric Lexer.
1911 -Initial use of homologous vein tissue in arterial reconstruction.
1918 -First blood transfusion.
The Timeline of Transplantation….
1949 -Establishment of US Navy Tissue Bank.
1954 -First successful living-related kidney transplant from identical twins performed by Dr. Joseph Murray and Dr. David Hume in Boston, MA. The recipient had normal kidney function for eight years.
1955 -Initial fresh heart valve allograft put into descending aorta.
1955 -Frozen venous allograft for femoral artery by.
1962 -First fresh heart valves implanted into cardiac position.
The Timeline of Transplantation….
1962 -First successful cadaveric kidney transplant by Dr. Joseph Murray and Dr. David Hume in Boston, MA. The recipient had normal kidney function for 21 months.
1963 -First liver transplant performed by Dr. Thomas Starzl..
1963 -First lung transplant performed by Dr. James Hardy at the University of Mississippi Medical Center, Jackson, MS.
1967 -First heart transplant performed by Dr. Christian Bernard at Groate Shure Hospital, South Africa. The recipient had normal heart function for 19 months.
1967 - First successful pancreas transplant performed by Dr. Richard C. Lillehei at the University of Minnesota.
The Timeline of Transplantation….
1968 -Brain death criteria created.
1968 -The Uniform Anatomical Gift Act. Legislation allows gift of organs to others.
1971 -Frozen heart valves used in allograft.
1971 -Introduction of cryo-preserved human skin allografts.
1972 -The Uniform Anatomical Gift Act establishes the Uniform Organ Donor Card as a legal document in all 50 states making it possible for anyone 18 years or older to legally donate his or her organs upon death.
The Timeline of Transplantation….
1972 -End Stage Renal Disease Act paves way for Medicare coverage of all kidney transplants.
1974 -First use of cryo-preserved venous allograft.
1978 -Cyclosporin begins testing.
1979 -Living related pancreas transplanted, Minneapolis, MN.
1981 -Brain death criteria expanded by President's Commission for Study of Ethical Problems in Medicine and Biomedical Research.
The Timeline of Transplantation….
1981 -First heart and lung transplant performed by Dr. Norman Shumway at Stanford University Medical Center, Stanford, CA.
1982 -Barney Clark receives the first permanent artificial heart at the University of Utah.
1983 -FDA approval of cyclosporine, the most successful antirejection medication developed to date.
1984 -First heart / liver transplant performed by Dr. Starzl at the Children's Hospital of Pittsburgh.
1984 -Baby Fae receives a walnut-sized baboon heart in an operation at Loma Linda University Medical Center. She was the first infant to receive an animal organ. Baby Fae lived for 21 days.
The Timeline of Transplantation….
1984 -National Organ Transplant Act (Public Law 98.507) establishes nationwide computer registry operated by the United Network for Organ Sharing (UNOS). The Act also authorizes financial for organ procurement organizations and outlaws purchase or sale of organs.
1985 -New York State, Oregon, and Pennsylvania Required Request Law. Mandates all potential organ and tissue donors be approached for donation. Soon thereafter, all remaining 47 states follow suit.
1986 -Consolidated Omnibus Budget Reconciliation Act ed. Requires all potential donors to be approached, superseding state laws and adding hospitals must comply to receive Medicare benefits.
The Timeline of Transplantation….
1988 -FDA approval of Viaspan or UW solution, greatly extends preservation time for livers.
1988 -t Commission on Accreditation of Health Care Organizations sets donor identification and notification standards. Requires the hospitals to have policies and procedures in place for the identification, referral and procurement of organs and tissues.
1989 -Dr. Thomas Starzl at the University of Pittsburgh reports clinical success of promising new anti-rejection drug, FK-506.
1989 -First liver transplant from a living related donor.
The Timeline of Transplantation….
1990 -Lung transplantation attempted as cure for Cystic Fibrosis.
1990 -Dr. Joseph Murray (performed first kidney transplant) awarded Nobel Prize for Medicine.
1990 -Dr. Thomas (pioneered bone marrow transplants as a cure for leukemia) awarded Nobel Prize for Medicine.
1990 -First successful heart related lung transplant.
1991 -First attempt at partial lung transplant.
The Timeline of Transplantation….
1991 -First successful small intestine transplant.
1996 -U.S. surgeons at Barnes Hospital in St. Louis, University of California, San Francisco, and Stanford University Hospital perform split-liver transplants.
Classification of grafts
Autografts: Self-tissue transferred from one body site eo another in the same individual. Isografts: Tissue transferred between genetically identical individuals. Allograft / Homograft: Tissue transferred between genetically different of the same species. Xenograft / Heterograft: Tissue transferred between different species.
Autografts and allograftts are usually accepted, owing to the genetic identity between graft and host.
Because an allograft is genetically dissimilar to the host, it is often recognized as foreign by the immune system and is rejected.
Xenografts exhibit the greatest genetic disparity and therefore engender a vigorous graft rejection.
Allograft acceptance
Histocompatibility & Histoincompatibility. Antigens determining histocompatibility: coded by 40 different loci. Loci responsible for most vigorous rejection is the Major Histocompatibility Complex (MHC). ( H2 in mice and HLA in humans) MHC loci is closely linked and is inherited as a complete set (haplotype) from each parent.
Allograft rejection
Rate varies according to tissue involved. Skin grafts are rejected faster than kidney or heart transplants.
Mechanism of rejection
Avrion Mitchison (1950) : lymphocytes but not serum antibody can transfer allograft immunity. Rats devoid of thymus can even accept xenografts. T cells derived from allograft primed mouse transfer second set allograft rejection to an unprimed syngenic recipient. Long survival of allografts in children suffering from thymic defeciancy.
T lymphocytes are involved in graft rejection.
Both T cell sub populations CD4 and CD8 are involved in graft rejection. Studied by blocking either of the sub populations by monoclonal antibodies directed against them. Blocking CD8 alone : Graft rejected in 15 days. Blocking CD4 alone: Graft rejected in 15- 30 days. Blocking both: Graft survived up to 60 days.
Mechanism of graft rejection….
Primarily by cell mediated immune response to alloantigen (MHC antigen). Both delayed type hypersensitivity and cell mediated cytotoxicity reactions have been implicated. Two stages involved: a) Sensitization phase. b) Effector phase.
Sensitization phase
CD4 and CD8 T cells recognize alloantigens. Both major and minor histocompatibility complexes are recognized. Recognize both donor MHC and a peptide with in the cleft. Peptide in the cleft in case of MHC I is derived from protein synthesized by the allogenic cell. In case of MHC II, proteins taken up and processed by the endocyrtic path way of the allogenic APCs, are bound to the cleft.
Host TH is activated when it interacts with an APC expressing an antigen ligand – MHC complex and also provides a requisite co-stimulatory signal. Different cell populations, within the graft serve as APCs. Dendritic cells have high levels of MHC II and function as major APCs. APCs of host origin migrate into graft, endocytose the foreign antigen and present them as processed peptides with self MHCs.
enger leukocytes
A population of donor APCs migrating from the graft to the regional lymph nodes. Primarily dendritic cells with high levels of MHC II & normal levels of MHC I. Wide spread in mammalian tissues except brain. Express allogenic MHC Ag. Recognized as foreign. Stimulate immune activation of T lymphocytes in lymph nodes.
Other APCs include: a) Langerhans cells b) Endothelial cells lining the blood vessels. These express MHC I and MHC II.
Recognition of alloantigens induce vigorous T cell proliferation. Major proliferating cell is the CD 4 T cell which recognizes MHC II directly or alloantigen peptides presented by APCs.
Effector phase
Delayed type hyper sensitivity. CTL mediated cytotoxicity. Antibody – compliment lysis. Antibody dependent cell mediated cytotoxicity (ADCC).
Influx of T cells and macrophages. Promoted by cytokines produced by TDTH cells. Recognition of foreign class alloantigens on th graft by CD 8 cells lead to CTL mediated killing. CD 4 cells function as MHC II restricted cytotoxic cells responsible for graft rejection.
Cytokines released by TH cells play central role. (IL 2, IFN γ & TNF β) IL 2 promotes T cell proliferation. Necessary for generation of CTLs. IFN γ promotes development of DTH response, Promotes influx of macrophages and subsequent activation of macrophages into more destructive cells. TNF β has direct cytotoxic effect on graft cell, Induces expression of MHC I and IIon graft cell.
CD 40 in allograft rejection
Expressed on wide variety of cells including dendritic cells, B cells, macrophages and endothelial cells. Critical role in allograft rejection. Inhibition of CD 40 with mAbs prolongs rejection of cardiac allografts and renal allografts. Hypothesized that CD 40 has a role in sensitization phase of T cell.
Modes of rejection
Hyper acute rejection. Acute early rejection. Acute late rejection. Chronic rejection.
Hyper acute rejection
Occurs within minutes of transplantation. Characterized by micro thrombi in capillaries and sludging of blood cells. Caused by pre existing host serum Abs specific for Ag of graft. Ag- Ab complex activates compliment resulting in intense infiltration of neutrophills into the grafted tissue. Causes massive blood clot in capillaries preventing vascularization of grafts.
Presence of Ab against Ag of graft
Recipients of repeated blood transfusion. Repeated pregnancies. Previous grafts. Specific for blood group antigens.
Rejection of xenografts follow this mode.
Accelerated rejection
A subtype of hyper acute rejection. Ab produced immediately after tranaplants.
Acute early rejection
Rejection within 10 days or so. Severe infiltration of the grafts by mononuclear cells. Rupture of capillaries. Involves T cell mediated reactions.
Acute late rejection
Rejection from 11th day onwards, in patients istrated with immunosupressiue drugs. Deposition of Immunoglobulins in blood vessel walls. Induce platelet aggrgation in capillaries. ADCC occurs.
Chronic rejection
Develops months or years after transplantation. After acute reaction has subsided. Includes both humoral and cell mediated response.
Tissue typing
Identification of HLA in donor and recipient tissue. Donor and recipient screened for ABO blood group compatibility.
Microcytotoxicity
WBCs from donor and recipient taken in wells of a microtitre plate. Abs against various MHC I and II Ags are added. Incubated for some time. Compliment is then added. Cytotoxicity assessed by uptake of dye. Indicates presence or absence of MHC Ag.
Mixed lymphocyte reaction (MLR)
To quantify the degree of compatibility. X ray irradiated or mitomicin C treated donor lymphocytes mixed with recipient lymphocytes. Medium contains H3 Thymidine. Checked for proliferation of T cells. T cell proliferation measured by the amount of H3 Thymidineinto cell DNA. Greater the differentiation, more the amount of H3 Thymidine. Time consuming.
Immunosupressive therapy
Generalised immunosupression of responses to all antigens. Slows down proliferation of activated lymphocytes. 3 processses i. Surgical process. ii. Irradiation. iii. Drugs.
Surgical process
Thymectomy. Spleenectomy. Lymphadenectomy.
Total lymphoid irradiation (TLI)
Lymphocytes are extremely sensitive to radiation. Recipient receives multiple x- ray exposure to thymus, spleen and lymph nodes before transplantation. 200 rads/day for several days before transplantation. Total of 3400 rads. Bone marrow not irrradiated. Lymphoid stem cells proliferate and renew population of circulating lymphocytes. New lymphocytes are tolerant to Ag of the graft.
Drugs
Azathioprine (imuran): mitotic inhibitor. istrated just before transplantation. Diminishes T cell proliferation. Metabolised to 6-mercaptopurine which is converted to 6-mercaptopurine riboside. Structurally similar to inosinic acid, precursor of purine biosynthesis. Acts as a competitive inhibitor in purine biosynthesis. Both B and T cell proliferation is diminished.
6-mercaptopurine
6- mercapto purine riboside phosphate
Inosine monophosphate
Cyclophosphamide: . Alkylating agent. . Inserts into DNA forming cross links. . DNA disrupted. . Effective against rapidly dividing cells. . Given at the time of grafting. . Blocks T cell proliferation.
Corticosteriods
. Prednisone and Dexamethasone. . Anti inflammatory. . Exerts effects at various levels of immune response.
Cyclosporin A & Rapamycin . Fungal metabolites . Has immuno supressive properties. . Blocks activation of resting T cells. . Inhibits transcription of gene coding for IL2 receptor (IL2R).
Specific immunosupressive therapy
Monoclonal Antibodies directed against various molecules of immune system. Manipulation of CD40. Agents blocking co – stimulatory signals. Donor treatment with mAbs against T cells.
Transplants
Corneal transplants. Kidney transplants. Heart transplants Liver transplants. Bone marrow transplants. Skin transplants. Pancreas transplants.
References
Immunology; 5th edition; Richard.A.Goldsby, Thomas.J.Kindt, Barbara.A.Osborne, Janis Kuby. An introduction to immunology; C.V.Rao. www.whfreeman.com/immunology5e http://www.novartis-transplant.com/ http://en.wikipedia.org/wiki/Organ_transplant http://www.eurotransplant.nl/?id=timeline
Thank you……….
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