About CXCL9

What is CXCL9 and why does it matter in primary HLH?

CXCL9 makes IFNγ-driven hyperinflammation measurable^1,2

Chemokine (C-X-C motif) ligand 9 (CXCL9) is a type of cytokine released almost exclusively by interferon gamma (IFNγ)-activated macrophages.¹ Its primary function is to attract T cells into inflamed tissues.²

IFNγ itself is difficult to reliably measure in the blood. CXCL9—which is more stable and easily measurable—is a surrogate marker of IFNγ activity.^1,2 CXCL9 measurement is a way to translate underlying immune activation into clinically meaningful information to support diagnosis and monitor disease activity.¹

Explore the digital deck of CXCL9 facts below

CXCL9 is induced almost exclusively by IFNγ.³ This downstream association provides a measurable marker of IFNγ-driven hyperinflammation, making it useful as an ancillary diagnostic tool.²

CXCL9 is more specific than traditional inflammatory markers

Traditional inflammatory markers such as ferritin, CRP, and LDH reflect broad immune activation.⁴ CXCL9 adds a more biologically specific signal of IFNγ-driven pathology to existing clinical assessments.²

CXCL9 testing is intended to complement, not replace, standard laboratory markers.⁴

CXCL9: A dynamic marker of disease activity

Currently, no universally accepted cutoff exists for CXCL9 levels.¹ Tracking CXCL9 level trends alongside standard laboratory markers can support an assessment of disease activity and trajectory.⁴

Download IFNγ and CXCL9 testing brochure

CXCL9 testing sites

There is growing recognition of testing for CXCL9 as a biomarker for IFNγ activity.² The following organizations offer CXCL9 testing to help with identifying primary HLH:

Machaon Diagnostics
Website	machaondiagnostics.com/test/cxcl9-level
Turnaround time	STAT: <24 hours Routine: <1 week
Lab hours	24/7
Phone	1-800-566-3462 510-839-5600
Fax	510-839-6153

Cincinnati Children’s Hospital
Website	testmenu.com/cincinnatichildrens/Tests/723501
Turnaround time	4 days
Lab hours	Mon-Fri, 8:00 AM to 5:00 PM (ET)
Phone	513-636-4685
Fax	513-636-3861

This is not an exhaustive list of labs offering CXCL9 testing. Please check for the availability of this test within your own institution prior to contacting these sites.

Other tests^5,6

In the absence of an underlying cause, such as malignancy, these tests can be useful for identifying the typical features of primary HLH.^5,6

Complete blood counts
Ferritin
ALT, bilirubin
IL-18

Fibrinogen/coagulation tests
Triglycerides (fasting)
sCD25

ALT=alanine transaminase; IL-18=interleukin-18; sCD25=soluble cluster of differentiation 25.

References

Rocco JM, Oved JH, Patel RJ, et al. CXCL9 as a novel prognostic marker to identify high-risk adults with hemophagocytic lymphohistiocytosis. Blood. 2026;147(9):960-972. doi:10.1182/blood.2025030976
De Benedetti F, Prencipe G, Bracaglia C, Marasco E, Grom AA. Targeting interferon-γ in hyperinflammation: opportunities and challenges. Nat Rev Rheumatol. 2021;17(11):678-691. doi:10.1038/s41584-021-00694-z
Bracaglia C, de Graaf K, Pires Marafon D, et al. Elevated circulating levels of interferon-γ and interferon-γ-induced chemokines characterise patients with macrophage activation syndrome complicating systemic juvenile idiopathic arthritis. Ann Rheum Dis. 2017;76(1):166-172. doi:10.1136/annrheumdis-2015-209020
Shakoory B, Geerlinks A, Wilejto M, et al. The 2022 EULAR/ACR points to consider at the early stages of diagnosis and management of suspected haemophagocytic lymphohistiocytosis/macrophage activation syndrome (HLH/MAS). Arthritis Rheumatol. 2023;75(10):1714-1732. doi:10.1002/art.42636
Henter JI, Horne A, Aricó M, et al. HLH-2004: diagnostic and therapeutic guidelines for hemophagocytic lymphohistiocytosis. Pediatr Blood Cancer. 2007;48(2):124-131. doi:10.1002/pbc.21039
HLH diagnosis strategy. Cincinnati Children's Hospital. Accessed August 18, 2026. https://www.cincinnatichildrens.org/service/h/hlh/clinical/test

What is CXCL9 and why does it matter in primary HLH?

CXCL9 makes IFNγ-driven hyperinflammation measurable^1,2

CXCL9 is more specific than traditional inflammatory markers

CXCL9: A dynamic marker of disease activity

CXCL9 testing sites

Other tests^5,6

INDICATIONS

IMPORTANT SAFETY INFORMATION

Infections

Increased Risk of Infection With Use of Live Vaccines

Infusion-Related Reactions

Adverse Reactions

Primary HLH

HLH/MAS

References

What is CXCL9 and why does it matter in primary HLH?

CXCL9 makes IFNγ-driven hyperinflammation measurable1,2

CXCL9 is more specific than traditional inflammatory markers

CXCL9: A dynamic marker of disease activity

CXCL9 testing sites

Other tests5,6

INDICATIONS

IMPORTANT SAFETY INFORMATION

Infections

Increased Risk of Infection With Use of Live Vaccines

Infusion-Related Reactions

Adverse Reactions

Primary HLH

HLH/MAS

References

CXCL9 makes IFNγ-driven hyperinflammation measurable^1,2

Other tests^5,6