LST Proliferation Assays

Question 1

Which radioactive compound is most commonly used to measure DNA synthesis in the tritiated thymidine incorporation assay for lymphocyte proliferation?

Accepted Answer

³H-thymidine

Answer

³H-thymidine (tritiated thymidine) is incorporated into newly synthesized DNA during cell division, making it the gold standard radiometric marker for lymphocyte proliferation assays.

Question 2

In the tritiated thymidine incorporation assay, what instrument is used to quantify the radioactivity incorporated into lymphocyte DNA?

Accepted Answer

Liquid scintillation counter

Answer

A liquid scintillation counter is used to measure the beta emissions from ³H-thymidine incorporated into DNA, providing counts per minute (CPM) as a measure of proliferation.

Question 3

CFSE (carboxyfluorescein succinimidyl ester) measures lymphocyte proliferation by which mechanism?

Accepted Answer

Progressive dilution of the dye with each cell division

Answer

CFSE covalently labels intracellular proteins, and with each cell division the dye is equally distributed between daughter cells, halving fluorescence intensity and allowing enumeration of division cycles by flow cytometry.

Question 4

The Stimulation Index (SI) in an LST proliferation assay is calculated as:

Accepted Answer

CPM of stimulated cells / CPM of unstimulated cells

Answer

The Stimulation Index is the ratio of radioactive incorporation (or other proliferation signal) in antigen-stimulated cells divided by that in unstimulated control cells, with a ratio ≥ 2–3 generally considered positive.

Question 5

What is the typical duration of lymphocyte culture before adding tritiated thymidine in a standard LST proliferation assay?

Accepted Answer

5–6 days

Answer

Lymphocytes are cultured for 5–6 days to allow sufficient antigen processing, T-cell activation, and clonal expansion before a tritiated thymidine pulse is added in the final 18–24 hours.

LST - Lymphocyte Stimulation Test Practice Test

LST - Lymphocyte Stimulation Test Practice Test

LST Proliferation Assays