IL-5 Reporter HEK 293 Cells

Cell line description

HEK-Blue™ IL-5 cells were generated by stable transfection with the genes encoding the human IL-5 receptor (IL-5Rα and IL-5RB chains), human STAT5b, and a STAT5-inducible secreted embryonic alkaline phosphatase (SEAP) reporter. The binding of IL-5 to its receptor triggers a signaling cascade leading to the activation of STAT5 and the subsequent production of SEAP. This can be readily assessed in the supernatant using QUANTI-Blue™ Solution, a SEAP detection reagent.

HEK-Blue™ IL-5 cells detect human (h) and mouse (m) IL-5 (see figures). Of note, these reporter cells also respond to hIFN-γ. However, they do not respond to other STAT5-signaling cytokines of the β-common chain family: IL-3 and GMCSF (see figures).

IL-5 background

Interleukin 5 (IL-5) is a secreted pro-inflammatory cytokine that specifically induces the differentiation of eosinophils, which play important roles in host defense as well as in pathologies such as allergies and asthma [1]. It also stimulates B cell growth and increases immunoglobulin secretion. Homodimeric IL-5 signals through the heterodimeric cell surface IL-5 receptor (IL‑5R) consisting of IL-5Rα (also called CD125) and IL-5RB, (also called the cytokine receptor common subunit beta, CSF2RB or CD131).
The binding of IL-5 to its receptor triggers three main signaling pathways: JAK/STAT, PI3K, and MAPK/ERK [1‑2]. Of note, monomeric IL-5 has no activity [2]. The pivotal role of IL-5 in eosinophil differentiation makes it an attractive target in eosinophilic conditions such as asthma [3].

Relevance to therapeutic development

Benralizumab is a humanized, afucosylated IgG1 monoclonal antibody (mAb) designed to target the alpha chain of the human interleukin 5 receptor (IL-5Rα), expressed on eosinophils and basophils [4]. This mAb is engineered with an afucosylated Fc region, which enhances its interaction with FcγRIIIa on natural killer (NK) cells, leading to strong antibody-dependent cell-mediated cytotoxicity (ADCC). This heightened ADCC activity significantly enhances eosinophil depletion, providing a robust and sustained therapeutic effect in eosinophilic diseases [5]. Benralizumab is FDA-approved for the treatment of severe eosinophilic asthma and eosinophilic granulomatosis with polyangiitis (EGPA) [6]. In addition to inhibiting interleukin-5 signaling, Benralizumab leads to eosinophil apoptosis through ADCC. In severe eosinophilic asthma, Benralizumab leads to rapid, near-complete depletion of eosinophils in blood and tissue, similar to the blood eosinophil depletion seen with oral prednisone. The ability of Benralizumab to deplete eosinophils in blood and tissue made it a suitable treatment option for EGPA [4,6].

1. Dougan M. et al., 2019. GM-CSF, IL-3, and IL-5 family of cytokines: regulators of inflammation. Immunity. 50(4):796-811.
2. Morris R. et al., 2018. The molecular details of cytokine signaling via the JAK/STAT pathway. Protein Sci. 27(12):1984-2009.
3. Yanagibashi T. et al., 2017. Allergic diseases: From bench to clinic - Contribution of the discovery of interleukin-5. Cytokine. 98:59-70.
4. Wechsler ME, et al., 2024. Benralizumab versus Mepolizumab for Eosinophilic Granulomatosis with Polyangiitis. N Engl J Med. 390(10):911-921.
5. Kolbeck R, et al., 2010. MEDI-563, a humanized anti-IL-5 receptor alpha mAb with enhanced antibody-dependent cell-mediated cytotoxicity function. J Allergy Clin Immunol. 125(6):1344-1353.e2.
6. Fasenra (benralizumab) US prescribing information; 2024. Available at: https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/761070s021lbl.pdf