Frequently Asked Questions

All samples should be prepared in FACS buffer.

FACS buffer composition:

• Phosphate-buffered saline (PBS)
• 1–5% protein (e.g., FBS, BSA, or serum)
• 2 mM EDTA (helps prevent cell clumping)

Yes. All samples must be filtered prior to running on any instrument.

• Fortessa/Symphony: Filter cells through at least a 70 µm mesh
• Cell sorters: Filter cells through a 35 µm or 40 µm mesh

Recommended option: 5 mL round‑bottom tubes with strainer caps
(e.g., Falcon tube #2235)

The Core does not routinely provide these tubes; however, a limited supply may be available if needed.

Analyzer (Symphony/Fortessa):

• Recommended concentration: 20 million cells/mL
• Minimum volume: 200 µL

Sorter (AriaFusion/SH800/MA900):

• Recommended concentration: up to 40 million cells/mL
• Minimum volume: 200 µL
• Please bring extra FACS buffer for dilution if needed

Dilution is preferred over concentration, as the Core does not currently have a centrifuge available.

Yes—both are required.

• Negative (unstained) controls allow assessment of background signal
• Single‑color controls are necessary for accurate compensation and fluorophore contribution assessment

Without appropriate controls, it becomes extremely difficult to correctly identify positive and negative populations or accurately define populations of interest.

Yes—adding buffer is strongly recommended.

Acceptable collection buffers include:

• Culture media
• FACS buffer
• RNA lysis buffer

Be aware that the collection buffer will be diluted by PBS from the instrument.

For questions about expected dilution volumes, please consult Core staff.

No. The facility operates on a first‑come, first‑served basis, and all experiments are treated equally.

You are welcome to:

• Ask other users if they expect to finish early
• Monitor the schedule for cancellations or released time

A user has the right to begin their experiment according to the published schedule.

While a user may voluntarily give up time, they are not obligated to do so.

• No Core staff are available after 5:00 PM to assist with experiments.
• Investigators requiring staff assistance outside normal hours should coordinate with Core staff in advance.

After‑hours access:

• Independent users of the Symphony, Fortessa, BioPlex and CTL Immunospot may use the lab after hours
• Approval is required—please refer to General Lab Policies for instructions on requesting after‑hours access

Yes, for specific instruments.

• Independent use is allowed on the Symphony, Fortessa, BioPlex, CTL Immunospot, SH800, and MA900
• Users must complete required training and be approved as independent users

Please visit the Training page for details on becoming an independent user.

The Core Facility is available to investigators across UTMB. External users may be accommodated on a case‑by‑case basis.

All users must register in the UTMB iLab system and receive approval before scheduling instrument time or services.

• Training is required for independent instrument use.
• Training is not required for staff‑assisted services, such as assisted acquisitions or cell sorting.

Yes. The Core offers consultation services for experimental design, antibody and fluorochrome panel design, data analysis, and FlowJo instruction.

All scheduling is conducted through the UTMB iLab system. Users select the desired instrument, choose a time slot, and provide billing information before confirming the reservation.

Yes. Trained users can request assisted use directly when creating a reservation in iLab by selecting the appropriate pricing option.

Users are billed based on actual instrument time used, as tracked by instrument time logs. Billing is processed monthly by PI, with invoices issued at the beginning of each month for the prior month’s usage.

Yes.

• Analyzers: 30‑minute minimum
• Sorters: 1‑hour minimum

Sorter appointments cancelled with less than 24 hours’ notice may incur a cancellation fee unless extenuating circumstances are approved by Core staff.

The Flow Cytometry and Cell Sorting Core Facility operates as a BSL‑2 laboratory.

Yes. All users working with BSL‑2 samples must complete required biosafety training and comply with UTMB biosafety policies.

Data are stored on instrument computers temporarily. Only three months of data is retained. Users are responsible for saving data to approved storage locations.

No. Use of USB or external storage devices is strictly prohibited. Please contact Core staff for assistance with data transfer.

Yes. The Core maintains a FlowJo Portal license that allows up to four simultaneous logins and can be accessed from anywhere with internet connectivity.

Yes. Investigators are expected to acknowledge the Flow Cytometry and Cell Sorting Core Facility in publications and presentations that include data generated using Core resources.

Yes. Core staff can provide standardized grant language, equipment descriptions, and letters of support upon request.