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Test Code FOXP3 PROT EXP FOXP3 Protein Expression

Important Note

This test is no longer offered as a clinical test. It is Research Use Only (RUO). For more information contact the Immunology Diagnostics Laboratory (IDL) at

Clinical System Name

FOXP3 Protein Expression





FOXP3 is a member of the forkhead family of transcriptional regulators and is required for the development of functional CD4+ CD25+ regulatory T cells.  This panel rules out Immune Dysregulation, Polyendocrinopathy, Endocrinopathy, X-Linked syndrome that is caused by mutations in FOXP3 gene.  The panel does so by looking at the amount of FOXP3 that CD4+ CD25+ cells are expressing and the quantity of CD4+, CD25hi, FOXP3hi Tregs present that are the most functionally suppressive.  It also looks at FOXP3 expression, in Helios+ cells that are thymically derived.

Sample Requirements

Specimen:  Whole Blood

Container(s):  Dark Green/Sodium Heparin (no serum separator)

Preferred Vol:  10-20 mL

Minimum Vol:  5-7 mL (for young children only)


Note: Specimens stable for only 24 hours at room temperature.


  Collected in-house at Seattle Children's Collected off-site (including SCH Bellevue)
M-Th collect any time collect any time
Friday must be received by main lab before 9 AM to ensure noon delivery to IDL must be received at IDL before 12 noon Friday
Saturday do not collect do not collect
day before a holiday ok if collected before 9 AM must be received at IDL before 12 noon day before holiday
Sunday ok if collected after 12 noon (to be tested next morning)

 ok if collected after 12 noon only if arrival at IDL before 12 noon next day

Sunday before a holiday Monday do not collect do not collect
Holiday ok if collected after 12 noon (to be tested next morning)

ok if collected after 12 noon only if arrival at IDL before 12 noon next day



Processing Instructions

Reject due to:  Clotted specimen, microtainers, refrigerated, samples >24 hours old

Spin:  N

Aliquot:  N

Temp:  RT

Storage location: Notify Sendouts Lab immediately.  Place whole blood in CPA room temp send-outs rack. Store extra labels in the clear plastic box attached to CPA refrigerator.


Off-site collection:  It is critical that samples be kept at room temperature; use extra packing to maintain temperature. If specimen will not arrive at Immunology Diagnostic Laboratory before noon for same day testing, blood should be drawn as late in the day as possible, maintained at room temperature and sent overnight to allow test set-up the following morning. Testing must be set up within 24 hours of collection. The lab accepts samples Monday through Friday but samples should be shipped only Monday through Thursday so they do not sit over the weekend. 


Transport samples at room temperature via overnight shipping to:

Seattle Children's Research Institute

Immunology Diagnostic Laboratory

1900 9th Avenue JMB-7

Seattle, WA 98101-1304


Temperature Time
Room temp 24 hours
Refrigerated N
Frozen N



STAT Performed TAT

Monday - Thurs; Friday must be in lab before noon

4-6 weeks

Limited specimen stability - see sample requirements

Performing Laboratory

Seattle Children's Laboratory    


Department:  Immunology Diagnostic Laboratory

Address:  1900 9th Avenue C9S-7, Seattle, WA 98101-1304

Phone: 206-987-7435


Lab Client Services: 206-987-2617,


Reference Range

Reference values accompany patient report.


Quantify FOXP3 and Helios expression in CD4+ CD25+ CD127- patient cells compared to normal cells. 


Method:  Flow Cytometry

Analytical Volume: 5 mL

CPT Codes

88184, 88185 (x4), 88187

Special Instructions

Links to: Immunology Diagnostic Laboratory


IDL Requistion