MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 40
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
Compared with myeloblasts, typical lymphoblasts show:
Lymphoblasts usually have a high N:C ratio, scant agranular blue cytoplasm and inconspicuous nucleoli. Myeloblasts more often show more cytoplasm, prominent nucleoli and sometimes granules or Auer rods.
The normal myeloid-to-erythroid (M:E) ratio in adult bone marrow is about:
Myeloid precursors normally outnumber erythroid precursors about 2–4 to 1. A low ratio suggests erythroid hyperplasia (e.g., hemolysis) or reduced myelopoiesis.
A cancer patient receiving G-CSF has WBC 35 × 10^9/L with toxic granulation, Döhle bodies and a few myelocytes. The best interpretation is:
G-CSF stimulates neutrophil production and release, giving neutrophilia, left shift and toxic changes that mimic infection. A history of growth factor use avoids misinterpretation.
Which pair of antigens is most useful for recognizing monocytes by flow cytometry?
Mature monocytes express CD14 and CD64 with CD11b and HLA-DR. CD3/CD7 are T-cell antigens, CD19/CD20 B-cell and CD41/CD61 platelet antigens.
A patient with recurrent venous thrombosis has a prolonged aPTT that does not correct on mixing with normal plasma and a positive dilute Russell viper venom time. Why is the aPTT prolonged in vitro?
Lupus anticoagulants bind phospholipid-protein complexes and prolong phospholipid-dependent tests in vitro, yet cause thrombosis in vivo. Factor VIII deficiency would correct on mixing and causes bleeding, not thrombosis.
For laboratory classification of antiphospholipid syndrome, a positive lupus anticoagulant, anticardiolipin or anti-beta-2 glycoprotein I result must be:
Antiphospholipid antibodies can appear transiently with infection or drugs, so persistence is required on two occasions at least 12 weeks apart. A positive ANA is not part of the criteria.
A 55-year-old man has nephrotic syndrome. Serum antibodies to the phospholipase A2 receptor (PLA2R) are positive. The most likely diagnosis is:
Anti-PLA2R antibodies are found in most cases of primary membranous nephropathy and help separate it from secondary forms. Anti-GBM disease is marked by anti-GBM antibodies with linear staining.
Cytotoxic T lymphocytes kill virus-infected target cells mainly by releasing:
Perforin forms pores in the target membrane and granzymes enter to trigger apoptosis. Major basic protein is an eosinophil product used against helminths.
During the neutrophil respiratory burst, which enzyme complex produces superoxide from molecular oxygen?
NADPH oxidase reduces oxygen to superoxide, which is converted to hydrogen peroxide. Myeloperoxidase then uses hydrogen peroxide to make hypochlorite; it does not make superoxide.
Differentiation of a naive CD4 T cell into a Th1 cell is mainly driven by which cytokine from dendritic cells and macrophages?
IL-12 induces T-bet and IFN-γ production, leading to Th1 cells that activate macrophages. IL-4 drives Th2 differentiation instead.
Besides TCR binding to peptide–MHC, full activation of a naive T cell requires a costimulatory signal between:
CD28 binding B7 molecules on activated antigen-presenting cells provides 'signal 2'. CD8 binds MHC class I, not class II.
CTLA-4, expressed on activated and regulatory T cells, mainly:
CTLA-4 competes with CD28 for B7 with higher affinity and delivers an inhibitory signal, limiting immune responses. The IL-2 receptor alpha chain is CD25.
For a B cell to switch from IgM to IgG production in response to a protein antigen, helper T cells must engage the B cell through:
CD40L on activated helper T cells binding CD40 on B cells, together with cytokines, drives class switching and germinal-centre formation. Absence of CD40L causes hyper-IgM syndrome.
Germinal centres, where B cells proliferate and undergo selection, are found in:
Antigen stimulation turns primary follicles into secondary follicles with germinal centres. Primary follicles contain resting naive B cells without germinal centres.
Peptides from viral proteins made in the cytosol are carried into the endoplasmic reticulum for loading onto MHC class I by:
Proteasome-generated peptides are pumped into the ER by TAP1/TAP2 and loaded onto class I molecules. The invariant chain and HLA-DM belong to the class II pathway.
A patient needs a stem cell donor. Assuming no recombination, what is the chance that one full sibling is HLA-identical to the patient?
HLA genes are inherited as two parental haplotypes; a sibling has a 1 in 4 chance of receiving the same two haplotypes. 50% is the chance of sharing exactly one haplotype.
Which of these immunoglobulin classes has the shortest half-life in serum?
Free serum IgE has a half-life of only about 2 days, although IgE bound to mast cells lasts much longer. IgG lasts about 21–23 days.
Serum for classical complement studies was accidentally collected in an EDTA tube. Classical pathway activity will be absent mainly because EDTA:
C1q, C1r and C1s need Ca²⁺ to stay assembled; the alternative pathway needs Mg²⁺, which EDTA also removes. Serum, not EDTA plasma, is the specimen for functional complement tests.
In the lectin pathway, mannose-binding lectin binds microbial carbohydrates and activates which enzymes to cleave C4 and C2?
MBL-associated serine proteases (MASPs) act like C1r/C1s and cleave C4 and C2 without antibody. Factor B and factor D belong to the alternative pathway.
The role of properdin in the alternative complement pathway is to:
Properdin (factor P) binds C3bBb and extends its half-life several-fold, amplifying C3 cleavage. Cleavage of factor B is done by factor D.