Flow Cytometry Principles Flashcards
7 cards from real SCYM practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Flow Cytometry Principles flashcards as text
Which gating hierarchy is standard for T-cell subset analysis in peripheral blood?
Answer: Lymphocytes → CD3+ → CD4+/CD8+
Standard T-cell gating proceeds from scatter-based lymphocyte gate → CD3+ T cells → CD4+ helper or CD8+ cytotoxic subsets.
What is autofluorescence in the context of flow cytometry, and how does it affect results?
Answer: Natural emission from cellular components that can mask dim fluorochrome signals
Autofluorescence from cellular components like flavins and NAD(P)H raises background fluorescence, reducing sensitivity for dim markers.
In cell cycle analysis using propidium iodide (PI), cells in G2/M phase appear as:
Answer: A peak at twice the G1 fluorescence intensity
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.
Which of the following correctly describes the role of Fc receptor blocking in flow cytometry?
Answer: It reduces non-specific antibody binding to Fc receptors on monocytes and NK cells
Fc receptor blocking agents (e.g., human IgG, FcR block) occupy Fc receptors on monocytes and NK cells to prevent non-specific antibody uptake.
What is the advantage of using a violet laser (405 nm) in addition to a blue laser (488 nm)?
Answer: It enables use of violet-excited dyes like BV421, expanding the number of detectable parameters
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.
When designing a multicolor flow cytometry panel, the brightest fluorochromes should be assigned to:
Answer: The most dimly or rarely expressed antigens
Bright fluorochromes maximize detection of low-density antigens, while dim antigens would be missed if paired with dim fluorochromes.
What does a bimodal distribution on a histogram suggest about an antigen's expression in a cell population?
Answer: Two distinct subpopulations exist: one positive and one negative for the antigen
A bimodal histogram indicates two distinct populations — one expressing the antigen (positive) and one not expressing it (negative), which is expected for many lineage markers.