SCYM Flow Cytometry Principles 5

Question 1

Which gating hierarchy is standard for T-cell subset analysis in peripheral blood?

Accepted Answer

Lymphocytes → CD3+ → CD4+/CD8+

Answer

Standard T-cell gating proceeds from scatter-based lymphocyte gate → CD3+ T cells → CD4+ helper or CD8+ cytotoxic subsets.

Question 2

What is autofluorescence in the context of flow cytometry, and how does it affect results?

Accepted Answer

Natural emission from cellular components that can mask dim fluorochrome signals

Answer

Autofluorescence from cellular components like flavins and NAD(P)H raises background fluorescence, reducing sensitivity for dim markers.

Question 3

In cell cycle analysis using propidium iodide (PI), cells in G2/M phase appear as:

Accepted Answer

A peak at twice the G1 fluorescence intensity

Answer

G2/M cells have doubled their DNA content compared to G1, so they incorporate twice as much PI and appear at double the fluorescence intensity.

Question 4

Which of the following correctly describes the role of Fc receptor blocking in flow cytometry?

Accepted Answer

It reduces non-specific antibody binding to Fc receptors on monocytes and NK cells

Answer

Fc receptor blocking agents (e.g., human IgG, FcR block) occupy Fc receptors on monocytes and NK cells to prevent non-specific antibody uptake.

Question 5

What is the advantage of using a violet laser (405 nm) in addition to a blue laser (488 nm)?

Accepted Answer

It enables use of violet-excited dyes like BV421, expanding the number of detectable parameters

Answer

A violet laser excites Brilliant Violet and Pacific Blue dyes that are not well excited at 488 nm, allowing additional parameters to be added to multicolor panels.

(SCYM) Specialist in Cytometry Practice Test

(SCYM) Specialist in Cytometry Practice Test

SCYM Flow Cytometry Principles 5