Flow Cytometry Basic Training

What Is Flow Cytometry? Flow ~ cells in motion Cyto ~ cell Metry ~ measure Measuring properties of cells while in a fluid stream

Flow Cytometry applications Flow Cytometry applications It can be used for…  Immunophenotyping  DNA cell cycle/tumor ploidy  Membrane potential  Ion flux  Cell viability  Intracellular protein staining  pH changes  Cell tracking and proliferation  Sorting  Redox state  Chromatin structure  Total protein  Lipids  Surface charge  Membrane fusion/runover  Enzyme activity  Oxidative metabolism  Sulfhydryl groups/glutathione  DNA synthesis  DNA degradation  Gene expression The use of flow in research has boomed since the mid-1980s

Models Year 1976FACS II 1991FACS Vantage 1998FACS Vantage SE 2000FACS DiVa 1980FACS IV/ FACS Aria Instruments model

Section II The 4 Main Components of a Flow Cytometer

What Happens in a Flow Cytometer? Cells in suspension flow single filepast Cells in suspension flow single file past a focused laser where they scatter light and emit fluorescence that is filtered and collected a focused laser where they scatter light and emit fluorescence that is filtered and collected then converted to digitized values that are stored in a file then converted to digitized values that are stored in a file Which can then be read by specialized software. Which can then be read by specialized software. Interrogation Fluidics Electronics Interpretation

What Happens in a Flow Cytometer (Simplified)

The Flow Cell Sheath Sample Stream Cell Hydrodynamic Focusing. The introduction of a large volume into a small volume in such a way that it becomes “focused” along an axis is called Hydrodynamic Focusing.

Forward Scatter FSC Detector Laser Beam

Side Scatter FSC Detector CollectionLens SSCDetector Laser Beam

Why Look at FSC v. SSC Since FSC ~ size and SSC ~ internal structure, a correlated measurement between them can allow for differentiation of cell types in a heterogenous cell population FSC SSC Lymphocytes Monocytes Granulocytes RBCs, Debris, Dead Cells

Fluorescence Detectors FSC Detector CollectionLens Laser Beam Fluorescence Detector A, B, C, etc…

Spectra of Common Fluorochromes Laser Lines (nm) PE-Texas Red Texas Red PI Ethidium PE FITC cis-Paranaric Acid

Filters Many wavelengths of light will be scattered from a cell, we need a way to split the light into its specific wavelengths in order to detect them independently. This is done with filters Optical filters are designed such that they absorb or reflect some wavelengths of light, while transmitting other. 3 types of filters  Long Pass filter  Short Pass filter  Band Pass filter

Long Pass Filters Transmit all wavelengths greater than specified wavelength  Example: 500LP will transmit all wavelengths greater than 500nm 400nm 500nm 600nm 700nm Transmittance

Short Pass Filter Transmits all wavelengths less than specified wavelength  Example: 600SP will transmit all wavelengths less than 600nm. 400nm 500nm 600nm 700nm Transmittance

Band Pass Filter Transmits a specific band of wavelengths  Example: 550/20BP Filter will transmit wavelengths of light between 540nm and 560nm (550/20 = 550+/-10, not 550+/-20) 400nm 500nm 600nm 700nm Transmittance

Dichroic Filters Can be a long pass or short pass filter Filter is placed at a 45º angle to the incident light Part of the light is reflected at 90º to the incident light, and part of the light is transmitted and continues on. DichroicFilter Detector 1 Detector 2

Example Channel Layout Dichroic Mirrors Bandpass Filters Detector#1 Detector#2 Detector#3 Detector#4

Detectors There are two main types of photo detectors used in flow cytometry  Photodiodes o Used for strong signals, when saturation is a potential problem (eg. FSC detector)  Photomultiplier tubes (PMT) o More sensitive than a Photodiode, a PMT is used for detecting small amounts of fluorescence emitted from fluorochromes.

Photoelectric Effect Einstein- Nobel Prize 1921

What is the puls?

Interpretation Once the values for each parameter are in a list mode file, specialized software can graphically represent it. The data can be displayed in 1, 2, or 3 dimensional format Common programs include…  CellQuest  Flowjo  WinMDI  FCS Express

Plots Contour Plot Density Plot Greyscale Density Dot Plot

Gating Is used to isolate a subset of cells on a plot Allows the ability to look at parameters specific to only that subset Can use boolean logic to include or exclude multiple gates

Gating Example

Flow Cytometry Data Smaller Region, Live cells mostly Larger Region includes all cells

Red Detector Blue Detector

PE detector

Red Detector Blue Detector

PE detector

References Numerous References available in the Flow Lab  Cytometry  Current Protocols in Flow Cytometry  Many more reference books available Purdue University Cytometry Laboratories website:  Dr. Robert Murphy, Carnegie Mellon University- Basic Theory 1 and 2 powerpoint slides The Scripps Research Institute Flow Cytometry Core Facility: