Q.1 What is the main immune response responsible for graft rejection?
Humoral immunity
Cell-mediated immunity
Innate immunity
Complement pathway
Explanation - T cells play a central role in recognizing and destroying transplanted tissues, making cell-mediated immunity the main response in graft rejection.
Correct answer is: Cell-mediated immunity
Q.2 Which type of transplant occurs between genetically identical individuals?
Allograft
Isograft
Autograft
Xenograft
Explanation - An isograft is a transplant between genetically identical individuals, such as identical twins.
Correct answer is: Isograft
Q.3 What is the role of HLA molecules in transplantation?
They prevent graft rejection
They mediate recognition of self vs. non-self
They block antibody production
They promote blood clotting
Explanation - Human Leukocyte Antigens (HLA) present antigens to T cells, making them key players in graft rejection.
Correct answer is: They mediate recognition of self vs. non-self
Q.4 Which type of graft is transplanted from one species to another?
Allograft
Isograft
Autograft
Xenograft
Explanation - A xenograft is a transplant between different species, such as pig heart valves into humans.
Correct answer is: Xenograft
Q.5 Hyperacute rejection is primarily mediated by:
T cells
NK cells
Preformed antibodies
Cytokines
Explanation - Pre-existing antibodies against donor antigens lead to hyperacute rejection, causing rapid graft failure.
Correct answer is: Preformed antibodies
Q.6 Which immunosuppressive drug inhibits calcineurin?
Tacrolimus
Azathioprine
Cyclophosphamide
Mycophenolate mofetil
Explanation - Tacrolimus inhibits calcineurin, preventing IL-2 transcription and T cell activation.
Correct answer is: Tacrolimus
Q.7 Which cytokine is most important in promoting T cell proliferation after transplantation?
IL-1
IL-2
IL-4
IL-10
Explanation - IL-2 is crucial for T cell proliferation and is a key target of immunosuppressive drugs.
Correct answer is: IL-2
Q.8 What type of rejection occurs weeks to months after transplantation?
Hyperacute rejection
Acute rejection
Chronic rejection
Immune tolerance
Explanation - Acute rejection occurs due to T cell-mediated immune responses within weeks to months post-transplant.
Correct answer is: Acute rejection
Q.9 Which graft is taken from the same individual?
Isograft
Allograft
Xenograft
Autograft
Explanation - An autograft uses tissue from the same person, such as skin grafts after burns.
Correct answer is: Autograft
Q.10 What is the most common target of immune recognition in transplantation?
MHC molecules
Complement proteins
Cytokines
IgM antibodies
Explanation - MHC (HLA in humans) is highly polymorphic and is the main target in transplant rejection.
Correct answer is: MHC molecules
Q.11 Which type of rejection develops gradually and is irreversible?
Hyperacute rejection
Acute rejection
Chronic rejection
Tolerant state
Explanation - Chronic rejection occurs over months to years and involves fibrosis and vascular damage, making it irreversible.
Correct answer is: Chronic rejection
Q.12 Bone marrow transplantation can lead to which complication?
Host vs. graft disease
Autoimmunity
Graft-versus-host disease
Hyperacute rejection
Explanation - In bone marrow transplantation, donor T cells attack recipient tissues, causing GVHD.
Correct answer is: Graft-versus-host disease
Q.13 Which complement pathway is most activated in hyperacute rejection?
Classical pathway
Alternative pathway
Lectin pathway
None
Explanation - Preformed antibodies activate the classical complement pathway, leading to hyperacute rejection.
Correct answer is: Classical pathway
Q.14 What is the major goal of immunosuppressive therapy in transplantation?
To kill all immune cells
To reduce infections
To induce tolerance while preventing rejection
To enhance antibody production
Explanation - The aim is to prevent graft rejection without completely paralyzing the immune system.
Correct answer is: To induce tolerance while preventing rejection
Q.15 Which drug blocks purine synthesis in lymphocytes?
Cyclosporine
Azathioprine
Tacrolimus
Corticosteroids
Explanation - Azathioprine is a purine analog that prevents DNA replication in lymphocytes, reducing rejection.
Correct answer is: Azathioprine
Q.16 Which cells directly destroy transplanted tissue?
B cells
CD4+ T cells
CD8+ T cells
NK cells
Explanation - CD8+ cytotoxic T cells recognize donor antigens on MHC I and directly lyse transplanted cells.
Correct answer is: CD8+ T cells
Q.17 What does 'mixed lymphocyte reaction' test for?
T cell proliferation to foreign MHC
Antibody cross-reactivity
Complement activation
Cytokine deficiency
Explanation - The mixed lymphocyte reaction measures T cell response to non-self MHC molecules.
Correct answer is: T cell proliferation to foreign MHC
Q.18 Which molecule is targeted by cyclosporine?
IL-2 receptor
Calcineurin
CD28
CD40
Explanation - Cyclosporine inhibits calcineurin, reducing IL-2 transcription and T cell activation.
Correct answer is: Calcineurin
Q.19 Which graft type is most common in organ transplantation?
Autograft
Isograft
Allograft
Xenograft
Explanation - Allografts, between genetically different members of the same species, are the most common in clinical practice.
Correct answer is: Allograft
Q.20 What is a major risk of long-term immunosuppressive therapy?
Decreased blood pressure
Infections and malignancies
Hyperimmunity
Excess RBC production
Explanation - Prolonged immunosuppression increases susceptibility to infections and cancer.
Correct answer is: Infections and malignancies
Q.21 Which molecule provides co-stimulation for T cell activation in graft rejection?
B7-CD28 interaction
IL-10
CD40-CD40L
MHC I
Explanation - Co-stimulation through B7 (on APC) and CD28 (on T cell) is essential for T cell activation in graft rejection.
Correct answer is: B7-CD28 interaction
Q.22 Which test is used to detect preformed antibodies against donor antigens?
ELISA
Flow cytometry crossmatch
PCR
Western blot
Explanation - Crossmatch testing detects donor-specific antibodies that can cause hyperacute rejection.
Correct answer is: Flow cytometry crossmatch
Q.23 Which is a feature of chronic rejection?
Thrombosis
Fibrosis and vascular occlusion
T cell cytotoxicity
Immediate graft loss
Explanation - Chronic rejection involves fibrosis and narrowing of blood vessels over months to years.
Correct answer is: Fibrosis and vascular occlusion
Q.24 Which immune cells are primarily involved in graft-versus-host disease?
Host T cells
Donor T cells
Host B cells
Donor NK cells
Explanation - In GVHD, donor T cells attack host tissues, causing damage in skin, liver, and GI tract.
Correct answer is: Donor T cells
Q.25 Which organ transplant has the highest chance of rejection without immunosuppression?
Heart
Kidney
Cornea
Liver
Explanation - Kidney transplants are highly immunogenic due to strong expression of HLA molecules.
Correct answer is: Kidney