MLT GlobeImmunology & Serology: Transplant & immunodeficiency
54 Immunology & Serology MCQs on Transplant & immunodeficiency with answers and explanations.
HIV infection progressively lowers which lymphocyte population, monitored by flow cytometry?
HIV binds CD4 with CCR5 or CXCR4 co-receptors and destroys helper T cells. A CD4 count below 200 cells/uL defines AIDS.
Which is NOT an immunodeficiency disorder?
Graves disease is autoimmune (TSH-receptor antibodies). SCID, DiGeorge and hyper-IgM syndrome are immunodeficiencies.
A burn patient receives skin taken from his own thigh. What type of graft is this?
Tissue moved from one site to another in the same individual is an autograft; it is genetically identical, so it is not rejected.
A kidney is donated between monozygotic twins. Which term applies, and why is rejection unlikely?
Identical twins share all HLA genes, so a graft between them (isograft/syngeneic graft) is accepted without immunosuppression.
Most clinical organ transplants, e.g. a kidney from an unrelated human donor, are classified as:
An allograft passes between genetically different members of the same species, so HLA mismatches can provoke rejection.
A porcine heart valve implanted in a human is an example of which type of graft?
Xenografts cross species; living xenografts face strong rejection, which is why porcine valves are chemically treated before use.
After an allogeneic stem-cell transplant, a patient develops rash, diarrhoea and raised liver enzymes. Graft-versus-host disease means:
In GVHD, immunocompetent donor T cells recognise host antigens as foreign, typically damaging skin, gut and liver. Recipient attack on the graft is rejection.
Why are siblings the most likely HLA-identical donors?
Each child inherits one parental haplotype from each parent as a block. Two siblings therefore have a 25% chance of sharing both haplotypes.
A 6-month-old boy has recurrent bacterial infections. Flow cytometry shows almost no CD19+ B cells, normal T cells and very low all immunoglobulin classes. The most likely diagnosis is:
Mutation in BTK blocks B-cell maturation, so B cells and all immunoglobulins are absent. Infections start after maternal IgG wanes around 6 months.
An infant with neonatal hypocalcaemia, a heart defect and low T-cell numbers most likely has:
22q11.2 deletion causes abnormal third and fourth pharyngeal pouch development: thymic hypoplasia (low T cells), absent parathyroids (hypocalcaemia) and conotruncal heart defects.
The most common primary immunodeficiency, which may cause anaphylaxis to transfused blood products if anti-IgA antibodies are present, is:
Selective IgA deficiency is the most common primary immunodeficiency and is often asymptomatic. Some patients make anti-IgA and need IgA-deficient or washed products.
A kidney recipient develops rising creatinine 3 weeks after transplant. Biopsy shows T lymphocytes infiltrating the tubules. The most likely process is:
Acute cellular rejection occurs days to months after transplant and is mediated by recipient T cells attacking donor tissue, seen as tubulitis. Hyperacute rejection occurs within minutes from preformed antibodies.
Years after a heart transplant, a patient shows gradual graft failure with concentric intimal thickening of graft arteries. This is:
Chronic rejection develops over months to years, with vascular intimal fibrosis (graft vasculopathy) and progressive loss of function. Hyperacute rejection happens within minutes of reperfusion.
Which loci code for HLA class II molecules?
Class II molecules are encoded by the DR, DQ and DP loci and are expressed on antigen-presenting cells. HLA-A, -B and -C are class I; complement genes are in the class III region.
Why must donor and recipient be ABO compatible for kidney transplantation?
Graft endothelium carries A and B antigens, so recipient anti-A or anti-B can cause hyperacute antibody-mediated rejection. ABO and HLA are separate systems.
A child with partial albinism and recurrent pyogenic infections has giant cytoplasmic granules in neutrophils on the blood film. The diagnosis is:
Chédiak-Higashi syndrome (LYST mutation) shows giant lysosomal granules, partial albinism and poor phagocyte killing. Chronic granulomatous disease has normal granule morphology.
Which laboratory finding is typical of untreated progressive HIV infection?
HIV destroys CD4+ T cells while CD8+ cells are often normal or increased, so the CD4:CD8 ratio falls below 1. B cells are present, often with polyclonal hypergammaglobulinaemia.
The HLA genes in humans make up the:
HLA (human leukocyte antigen) is the name of the human major histocompatibility complex, which strongly influences transplant compatibility.
For kidney transplantation, matching is traditionally most important at which HLA loci?
HLA-A, -B and -DR are the loci classically considered in kidney matching; mismatches at these loci have the greatest effect on graft survival.
How is a person's HLA inherited?
HLA genes are inherited as haplotypes, one from each parent, and both are expressed. This is why siblings have a 25% chance of being HLA-identical.