MLT GlobeDOH exam preparation (Abu Dhabi) – page 11
700 practice MCQs for the DOH medical laboratory exam. Level: Basic to intermediate.
Which immunoglobulin class gives the strongest agglutination?
Pentameric IgM has 10 binding sites, allowing it to bridge cells efficiently.
In secretions, which antibody usually exists as a dimer?
Secretory IgA is a dimer linked by J chain with a secretory component.
Which immunoglobulin does the fetus produce first?
The fetus produces IgM first and is protected by maternal IgG.
In mammals, which organ corresponds to the avian bursa of Fabricius?
B cells mature in the bone marrow. The thymus is where T cells mature.
Which is NOT a human immunoglobulin class?
The five classes are IgG, IgA, IgM, IgD and IgE; IgF does not exist.
IgA differs from other immunoglobulins in that it:
IgA is the main antibody at mucosal surfaces, blocking pathogen attachment.
C1 is activated in the classical pathway by:
C1q binds the Fc of antigen-bound IgG or IgM. Factor B belongs to the alternative pathway.
Complement enhances phagocytosis mainly through:
C3b coats microbes and binds complement receptors on phagocytes.
Which feature characterizes acquired immunity?
Adaptive immunity is specific, has memory and discriminates self from non-self.
The main advantage of passive immunization over active immunization is that it:
Preformed antibodies protect at once but are short-lived.
Memory cells develop from:
Both B and T lymphocytes form memory cells.
Which cells shut down immune responses after antigen is cleared?
Regulatory T cells suppress responses through IL-10 and TGF-beta.
Lymphokines are best defined as:
Lymphokines are lymphocyte-derived cytokines, including many interleukins and interferon-gamma.
The Arthus reaction is which type of hypersensitivity?
The Arthus reaction is a local immune complex reaction with vasculitis.
In Rh haemolytic disease of the fetus and newborn, which maternal immunoglobulin class crosses the placenta to destroy fetal red cells?
Only IgG is actively transported across the placenta via FcRn. Anti-D IgM, though produced first, is too large to cross.
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.
Which of these tests does NOT rely on an antibody tagged with an enzyme, fluorochrome or radioisotope?
The Coombs test is read as visible red-cell agglutination with unlabelled anti-human globulin. ELISA, IF and RIA each use a labelled antibody or antigen.
How much sodium hydroxide (MW 40) is needed to prepare 1 litre of N/5 (0.2 N) NaOH?
For NaOH the equivalent weight equals 40 g. 0.2 N × 40 g/L = 8.0 g per litre. 4 g would give 0.1 N.
Yellow discoloration of skin and sclera (jaundice) is due to:
Jaundice appears when bilirubin exceeds about 2-3 mg/dL. ALT indicates liver cell injury but does not cause yellow color.
Oxytocin mainly causes contraction of smooth muscle in which organ?
Oxytocin drives uterine contractions in labour and myoepithelial contraction for milk ejection. It has little effect on gut or vascular smooth muscle.