Rules-Based Medicine

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Interleukin-5 (IL-5)

Ultrasensitive Immunoassay


Rules-Based Medicine’s (RBM) internally developed and manufactured ultrasensitive immunoassay to interleukin-5 (IL-5) based on the Simoa® bead technology can accurately quantitate sub-pg/mL levels of IL-5 in human serum and plasma. Ultrasensitive IL-5 detection may be useful for clinical studies related to asthma and other eosinophilic disorders.

IL-5 is a homodimeric glycoprotein produced by T cell helper type 2 (TH2) cells, mast cells, eosinophils, CD34+ progenitor cells, epithelial cells, natural killer (NK) T cells, and type 2 innate lymphoid cells. The receptor is a heterodimer comprised of IL-5Rα -subunit and the common beta chain (βc) subunit. The IL-5Ra is expressed on all eosinophils. IL-5 is critical for development, survival, and maintenance of B cells and eosinophils. In combination with IL-4 and IL-13, IL-5 plays a critical role in vascular permeability, smooth muscle contractility, and IgE production. Overproduction of IL-5 is involved in various chronic inflammatory conditions, including allergic rhinitis, eosinophilic asthma, hyper-eosinophilic syndrome, eosinophilic esophagitis, and eosinophilic granulomatosis with polyangiitis.

The central role of IL-5 in eosinophil biology, its pathological role in many eosinophilic-mediated diseases, and the expression of IL-5Ra on eosinophils, makes it a very attractive therapeutic target. Several neutralizing monoclonal antibodies directed against IL-5 (mepolizumab and reslizumab) and its receptor IL-5Rα (benralizumab) are effective in treating eosinophilic asthma. RBM’s Simoa IL-5 ultrasensitive immunoassay is a critical tool in clinical studies evaluating the efficacy and safety of these and other similar biologics in diseases characterized by unregulated eosinophil activity.


Swiss-Prot Accession Number: P05113

Simoa™ Services
Biomarker LLOQ*
(Serum and Plasma)
(Undiluted Samples)
Volume Required
Serum or plasma Other fluids**
Interleukin-5 (IL-5) 0.052 pg/mL 0.026 pg/mL 150 µL 150 µL

* Lower limit of quantitation (LLOQ) represents the lowest amount of an analyte that can be quantitatively determined with acceptable precision. LLOQ is determined by performing 2-fold serial dilutions of Standard to be tested in triplicate over three runs. The percent coefficient of variation (CV) is calculated for each of the dilution replicates, and the LLOQ is determined as the concentration at which the CV is 30%.

** Cerebrospinal fluid, urine, tissue culture supernatants,  bronchoalveolar lavage, synovial fluid, tissue extracts, tears, skin washings, etc.

All assay services are performed in our CLIA-certified laboratory.
Intended for Research Use Only.