Thymus transplantation
Encyclopedia
Thymus transplantation is a form of organ transplantation where the thymus
is moved from one body to another.
, which results in an absent or hypoplastic thymus, in turn causing problems with the immune system
's T-cell mediated response. It is exclusively used in people with complete DiGeorge anomaly, which are entirely athymic. This subgroup represents less than 1% of DiGeorge syndrome patients.
Nezelof syndrome
is another thymus-related disease where it can be used.
of 75%, having a follow-up as long as 13 years.
Complications include an increased susceptibility to infections while the T cells have not yet developed, rashes and erythema.
(GVHD): First, it could cause a donor T cell-related GVHD, because of T cells from the donor that are present in the transplanted thymus that recognizes the recipient as foreign. Donor T cells can be detected in the recipient after transplantation, but there is no evidence of any donor T cell-related graft-versus-host disease.
Second, a thymus transplantation can cause a non-donor T cell-related GVHD because the recipients thymocyte
s would use the donor thymus cells as models when going through the negative selection
to recognize self-antigens, and could therefore still mistake own structures in the rest of the body for being non-self. This is a rather indirect GVHD because it is not directly cells in the graft itself that causes it, but cells in the graft that make the recipient's T cells act like donor T cells. It would also be of relatively late-onset because it requires the formation of new T cells. It can be seen as a multiple-organ autoimmunity in xenotransplantation
experiments of the thymus between different species. Autoimmune disease is a frequent complication after human allogeneic thymus transplantation, found in 42% of subjects over 1 year post transplantation. However, this is partially explained by that the indication itself, that is, complete DiGeorge syndrome, increases the risk of autoimmune disease.
Thymus
The thymus is a specialized organ of the immune system. The thymus produces and "educates" T-lymphocytes , which are critical cells of the adaptive immune system....
is moved from one body to another.
Indication
Thymus transplantation can be used to treat infants with DiGeorge syndromeDiGeorge syndrome
22q11.2 deletion syndrome, which has several presentations including DiGeorge syndrome , DiGeorge anomaly, velo-cardio-facial syndrome, Shprintzen syndrome, conotruncal anomaly face syndrome, Strong syndrome, congenital thymic aplasia, and thymic hypoplasia is a syndrome caused by the deletion of a...
, which results in an absent or hypoplastic thymus, in turn causing problems with the immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
's T-cell mediated response. It is exclusively used in people with complete DiGeorge anomaly, which are entirely athymic. This subgroup represents less than 1% of DiGeorge syndrome patients.
Nezelof syndrome
Nezelof syndrome
Nezelof syndrome is an autosomal recessive congenital immunodeficiency condition due to underdevelopment of the thymus.An association with CD44 has been proposed.-History:...
is another thymus-related disease where it can be used.
Effects and prognosis
A study of 54 DiGeorge syndrome infants resulted in all tested subjects having developed polyclonal T-cell repertoires and proliferative responses to mitogens. The procedure was well tolerated and resulted in stable immunoreconstitution in these infants. It had a survival rateSurvival rate
In biostatistics, survival rate is a part of survival analysis, indicating the percentage of people in a study or treatment group who are alive for a given period of time after diagnosis...
of 75%, having a follow-up as long as 13 years.
Complications include an increased susceptibility to infections while the T cells have not yet developed, rashes and erythema.
Graft-versus-host disease
Theoretically, thymus transplantation could cause two types of graft-versus-host diseaseGraft-versus-host disease
Graft-versus-host disease is a common complication after a stem cell transplant or bone marrow transplant from another person . Immune cells in the donated marrow or stem cells recognize the recipient as "foreign". The transplanted immune cells then attack the host's body cells...
(GVHD): First, it could cause a donor T cell-related GVHD, because of T cells from the donor that are present in the transplanted thymus that recognizes the recipient as foreign. Donor T cells can be detected in the recipient after transplantation, but there is no evidence of any donor T cell-related graft-versus-host disease.
Second, a thymus transplantation can cause a non-donor T cell-related GVHD because the recipients thymocyte
Thymocyte
Thymocytes are hematopoietic progenitor cells present in the thymus. Thymopoiesis is the process in the thymus by which thymocytes differentiate into mature T lymphocytes. The primary function of thymocytes is the generation of T lymphocytes . The thymus provides an inductive environment, which...
s would use the donor thymus cells as models when going through the negative selection
Negative selection
Negative selection may refer to:*Negative selection , in natural selection it refers to the selective removal of rare alleles that are deleterious...
to recognize self-antigens, and could therefore still mistake own structures in the rest of the body for being non-self. This is a rather indirect GVHD because it is not directly cells in the graft itself that causes it, but cells in the graft that make the recipient's T cells act like donor T cells. It would also be of relatively late-onset because it requires the formation of new T cells. It can be seen as a multiple-organ autoimmunity in xenotransplantation
Xenotransplantation
Xenotransplantation , is the transplantation of living cells, tissues or organs from one species to another. Such cells, tissues or organs are called xenografts or xenotransplants...
experiments of the thymus between different species. Autoimmune disease is a frequent complication after human allogeneic thymus transplantation, found in 42% of subjects over 1 year post transplantation. However, this is partially explained by that the indication itself, that is, complete DiGeorge syndrome, increases the risk of autoimmune disease.