Interleukin-5 (IL-5) (IL-5)

Interleukin-5 (IL-5) is a hematopoietic cytokine that plays a specialized role in the regulation of eosinophil biology (UniProt: P05113). It is primarily secreted by T-helper 2 (Th2) cells, mast cells, and group 2 innate lymphoid cells (ILC2s). IL-5 is the most potent cytokine for the differentiation, maturation, recruitment, and activation of eosinophils, which are key effector cells in allergic inflammation (PubMed: 27130435). In healthy states, it helps regulate immune responses against parasites, but its overproduction is a hallmark of eosinophilic diseases. In conditions such as severe eosinophilic asthma and hypereosinophilic syndromes, elevated levels of IL-5 drive pathological eosinophilia, leading to airway remodeling and tissue damage (NIH: StatPearls). Therapeutic monoclonal antibodies such as mepolizumab and reslizumab target and neutralize circulating IL-5, effectively reducing eosinophil counts in the blood and tissues. This neutralization prevents IL-5 from binding to its receptor, thereby improving clinical outcomes and reducing exacerbations in patients with severe eosinophilic disease.

Other names

Eosinophil differentiation factorEDFB-cell differentiation factor IBCDFIT-cell replacing factorTRF

Neutralization of the IL-5 cytokine to prevent its binding to the IL-5 receptor alpha (IL-5RA) subunit on the surface of eosinophils, thereby inhibiting the signaling pathways required for eosinophil maturation, recruitment, and survival.