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Life Technologies CountBright™ Absolute Counting Beads

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Many flow cytometers cannot directly provide the cell concentration or absolute count of cells in a sample. Absolute cell counts are generally obtained either by combining a separate cell concentration determination from a hematology analyzer with flow cytometric population data (multiple platform testing) or by adding an internal microsphere counting standard to the flow cytometric sample (single platform testing).

Invitrogen now offers CountBright™ Absolute and AccuCheck flow cytometry cell counting beads.

CountBright™ Absolute Counting Beads

CountBright™ Absolute flow cytometry cell counting beads are a calibrated suspension of microspheres that are brightly fluorescent across a wide range of excitation and emission wavelengths and contain a known concentration of microspheres. Countbright ™ Absolute flow cytometry cell counting beads are similar in size to lymphocytes, so they do not require any changes in instrument settings. For absolute counts, a specific number of counting beads are added to a known volume of sample, so the sample volume per bead is known. The number of beads in a sample tells you the volume analyzed, and allows accurate calculation of cells per microliter in the sample.

The CountBright Absolute flow cytometry cell counting beads give you:
  • Compatibility—with every commercially available instrument because they are loaded with a wide breadth of fluorochromes,
  • Versatility—easy to use protocol that works with multiple cell types including lyse/no wash whole blood
  • Accuracy—more reliable than multiple platform testing

Figure 1. Determination of live and dead cells and absolute cell number. Plot of calcein fluorescence collected with a 530/30 nm bandpass filter vs. ethidium homodimer-1 fluorescence, collected with a 610/20 nm bandpass filter, showing clear separation of live and dead cells, as well as counting beads. A mixture of live and heat-killed Jurkat cells (human T cell leukemia) was treated with the reagents in the LIVE/DEAD® Viability/Cytotoxicity Kit; CountBright™ Absolute Counting Beads were added, and the sample was analyzed by flow cytometry using 488 nm excitation.

DescriptionEx (nm)Em (nm)QuantityCat. No.
CountBright™ Absolute Counting Beads UV-635 385-800 5 mL C36950


AccuCheck Counting Beads

AccuCheck flow cytometry cell counting beads are ideal for clinical applications.  They offer a single-platform method for absolute cell counts that combines the advantages of direct flow cytometric immunophenotyping with the use of two different fluorescent beads that serve as a double internal control for pipetting and  mixing.  A known volume of AccuCheck flow cytometry cell counting beads is added to a known volume of cell sample and the beads are counted along with the cells.  Since the concentration of the beads is known, the number of cells/µL is obtained by relating the number of cells counted to the total number of fluorescent bead events.

The AccuCheck Counting Beads give you:

  • Accuracy—internal control using ratio of two different color beads indicates pipetting accuracy
  • Reliability—Single Platform is preferred over  multiple platform testing leading to consistency in results
  • Compatiblity—Easy to validate with most immunophenotyping experiments
DescriptionEx (nm)Em (nm)QuantityCat. No.
AccuCheck Flow Cytometry Counting Beads Bead A: 488
Bead B: UV-635
Bead A: 525-670
Bead B: 525-670
10 mL PCB100