Shynra - Transplant Questions Flashcards
A 23-year-old female has HLA genotype A3/A8, B1/B8, C4/C1. For each locus, the maternal allele is listed first and the paternal allele second. Several potential donors are available for an organ graft. Which of the following donors would be the closest match?
a. Donor A: A8/A27, B24/B8, C4/C9
b. Donor B: A3/A3, B27/B8, C1/C1
c. Donor C: A8/A6, B44/B8, C4/C1
d. Donor D: A6/A27, B1/B8, C4/C2
e. Donor E: A3/A8, B1/B27, C9/C4
b. Donor B: A3/A3, B27/B8, C1/C1
The answer is B. The closest match will have the fewest mismatched HLA genes not present in the recipient. For donor B, only HLA 827 is not already present in the recipient. Donor A has three mismatches, Donor C has two mismatches, Donor D has three mismatches, and Donor E has two mismatches.
A 6-year-old male receives a bone marrow transplant from his father during treatment tor acute myelogenous leukemia. Of primary concern will be the potential development of
a. acute rejection.
b. an allergic reaction.
c. autoimmune responses.
d. graft-versus-host disease.
e. immediate hypersensitivity.
d. graft-versus-host disease.
The answer is D. Graft-versus-host (GVH) disease is a risk because bone marrow contains immunocompetent cells. The GVH response is directed against host antigens that are not present in the donor bone marrow. Recipients of bone marrow transplants are usually immune- compromised or immunosuppressed, resulting in little risk for development of host-versus-graft responses such as acute rejection. Allergic reactions, also described as type I or immediate hypersensitivity reactions, do not occur in response to bone marrow transplantation. An autoimmune response is one directed by the immune system against self-antigens.
What are the possible ABO blood types of children to the union of a man who has blood type AB and a woman who has blood type O?
a. A only
b. A and B only
c. A, B, and AB only
d. A, B, AB, and O
e. O only
b. A and B only
The answer is B. Blood types A and B are both possible in children of parents with type AB and type 0. The genders of the parents and of the children are inconsequential because inheritance of ABO blood group is autosomal. A and B are codominant and are both dominant to 0. In this example, children will inherit either the A or B allele from the father and the 0 allele from their mother and will have either blood type A or blood type B. Inheritance of both A and B or of 0 only is not possible, eliminating types AB and 0 as possible blood types among the children of this couple.
Several types of immunologic rejection reactions can occur after organ transplantation. The rejection reaction that is caused by the presence of preformed antibodies in the recipient is referred to as
a. acute
b. hyperacute
c. chronic
d. immediate
e. accelerated
b. hyperacute
The answer is B. Hyperacute rejection of a transplanted organ occurs when the recipient’s preformed antibodies attack the donor organ, causing a rapid vascular spasm, vascular occlusion, and lack of organ perfusion by the recipient’s blood. This could occur in the case of an ABO blood group mismatch, in which a donor organ containing blood group A or group B antigens is transplanted into a patient who has preformed anti -A or anti-B antibodies. This is avoided by blood group matching before transplantation. A similar hyperacute rejection reaction can result with human leukocyte antigen (HLA) mismatch, in which the recipient has preformed antibodies to a HLA in the donor organ.
Class I human leukocyte antigens (HLAs) can be best described as
a. cell-surface proteins that contain HLA-A, HLA-B, and HLA-C determinants
b. substances involved in macrophage interactions with B cells
c. complement components
d. antigens involved in the inductive (sensitization) phase of cell-mediated cytolysis (CMC)
e. antigens principally responsible for the graft-versus-host (GVH) reaction
a. cell-surface proteins that contain HLA-A, HLA-B, and HLA-C determinants
The answer is A. Class I histocompatibility antigens are cell surface membrane proteins that contain human leukocyte antigen (HLA)-A, HLA-B, or HLA-C determinants. These antigens are involved in the effector phase of cell-mediated cytolysis (CMC) and in graft rejection. In both these processes, class I antigens are the major antigens by which the effector cells, cytotoxic T (Tc) cells, recognize target tissues. Class II antigens are the histocompatibility antigens involved in the presentation of antigen to T cells and B cells by macrophages. By a principle referred to as major histocompatibility complex (MHC) restriction, the macrophage must bear a class II antigen identical to that expressed on the B-cell membrane. Class III antigens include, among other substances, complement components C2, C4, and factor B; class III antigens are not involved in histocompatibility.
As compared to T cells, B-cell membranes are rich in which of the following antigens?
a. Class I human leukocyte antigens (HLAs)
b. Class II HLAs
c. Class Ill HLAs
d. HLA-B antigens
e. Complement-activating antigens
The answer is B. B-cell membranes are rich in class II human leukocyte antigens (HLAs), which also are found in macrophage membranes and in the membranes of activated peripheral blood T cells. Class I HLAs, including HLA-B antigens, are found on all lymphocytes and macrophages. In fact, class I HLAs are found on all nucleated cells except sperm and trophoblasts. Class III HLAs are not involved in histocompatibility but are complement components, specifically C2, C4, and factor B; class III genes also code for tumor necrosis factors and for cytochrome hydroxylases.
Which of the following tests can be used for typing of class I histocompatibility antigens?
a. Cell-mediated lympholysis
b. Donor-recipient mixed lymphocyte response
c. Primed lymphocyte typing
d. Mixed lymphocyte response with homozygous typing cells
e. Antibody- and complement-mediated cytotoxicity
The answer is E. Class I antigens are also called serologically defined antigens because they can
be identified by serologic tests. Class I antigens are detected by incubating lymphocytes with antisera specific to human leukocyte antigens (HLA)-A, -B, or -C. In the presence of complement, the antibody-sensitized cells are killed and the resultant membrane changes can be detected by the uptake of eosin or trypan blue, both of which are excluded from live cells.
Chronic graft rejection may be caused by
a. T cells
b. antibodies
c. T cells and antibodies
d. T cells and macrophages
e. Natural killer cells
The answer is D. Chronic graft rejection is caused by delayed-type hypersensitivity with involvement of tissue macrophages and T cells. The antigens involved in chronic graft rejection usually are antigens in minor histocompatibility loci (i.e., weak antigens not coded for by the human - leukocyte antigen (HLA) complex).
Graft-versus-host (GVH) disease would occur from a poorly matched bone marrow transplant rather than from a similarly matched kidney transplant because the kidney
a. expresses few donor class I human leukocyte antigens (HLAs)
b. expresses few donor class II HLAs
c. contains few donor erythrocytes
d. contains few donor B cells
e. contains few donor T cells
The answer is E. The kidney contains practically no T lymphocytes and, therefore, it is not likely to induce graft-versus- host (GVH) disease. After the organ is removed from the donor, it is perfused to remove all donor blood in its vasculature before its implantation. The bone marrow cannot be similarly purged of donor blood and must instead be treated with anti-thymocyte serum to remove the immunologically reactive cells.
Donor-recipient graft compatibility is determined through evaluation of which of the following?
a. Class I human leukocyte antigens (HLAs), ABO blood group, and antibodies to donor lymphocytes
b. Class II HLAs, ABO blood group, and antibodies to donor lymphocytes
c. Both class I and class II HLAs, ABO blood group, and antibodies to donor lymphocytes
d. Class Ill HLAs, ABO blood group, and antibodies to donor lymphocytes
e. ABO blood group and antibodies to donor lymphocytes
The answer is C. Class III human leukocyte antigens (HLAs) code for nonhistocompatibility antigens such as C2 and C4 of the complement system and are not involved in the graft rejection. The ABO blood group antigens are significant in the determination of histocompatibility. ABO blood group compatibility must exist between donor and recipient; crossing the blood group barrier compromises graft survival and may lead to hyperacute rejection. Typing of class I and class II HLAs also must be performed in the evaluation of donor- recipient compatibility. This is done through cytotoxicity assays, including the lymphocytotoxicity test. In this test, cytotoxic antibodies in serum from a sensitized recipient react with cell-surface antigens on donor lymphocytes, so that the lymphocyte cell membrane disintegrates and the cell dies. The reaction is detectable because dye is specifically absorbed by damaged and dying cells. Such a reaction would negate the use of that particular donor. In the blastogenesis assay, which is based on the mixed lymphocyte reaction, lymphocytes from both the prospective donor and the recipient are cultured and observed for reactions.
The cornea is considered to be privileged tissue because
a. it contains few human leukocyte antigens (HLAs)
b. it contains abundant HLAs
c. it is non-vascularized tissue
d. it is vascularized tissue
e. it is coated with enhancing antibodies
The answer is C. The cornea is “privileged” tissue only when the transplant procedure is conducted in a manner such that its non-vascularized status is not breached. The eye chamber is considered overall to be a privileged site in that all of its contents remain sequestered from T lymphocytes circulating in the vasculature. Even in the absence of corneal transplantation, an autoimmune attack can result if the eye is traumatized and the T cells of an individual are allowed to enter the chamber.
Which of the following transplants involves a transfer of skin from the thigh to the face?
a. Allogeneic
b. Autologous
c. Heterogenic
d. ldiotypic
e. Syngeneic
The answer is B. The transfer of skin from the thigh to the face in the same person is an autograft, which involves the transfer of autologous tis-sue. Autografts are done in plastic surgery to repair burn wounds, for example. Bone is commonly used in autograft procedures to promote healing of nonunited fractures, to restore structural integrity to the skeleton, and to facilitate cosmetic repair, as in facial reconstruction, where pieces of bone from the hip are used to rebuild portions of the face damaged by accident or malignancy. Allogeneic bone grafts also
are performed; these involve the transfer of bone between genetically dis- similar members of the same species. For this purpose, the bone is aseptically removed , sterilized by ethylene oxide or gamma irradiation, and frozen. Freezing is used for all bone tissue transplants except fresh autografts because it reduces immunogenicity.
A cadaver kidney transplant can be characterized as which of the following types of transplants?
a. Allogeneic
b. Autologous
c. Heterogenic
d. ldiotypic
e. Syngeneic
The answer is A. Transplanting a cadaver kidney is a relatively standard procedure that uses allogeneic tissue to replace a patient’s diseased organ.
