IL5 (Interleukin-5) is a Th2 cytokine critical for eosinophil development, recruitment, and activation. While primarily known for its role in allergic inflammation and asthma, IL-5 also has important functions in immune regulation and has been detected in the central nervous system. In neurodegenerative diseases, IL-5 has complex and sometimes paradoxical roles, exhibiting both pro-inflammatory and potential protective properties[1][2].
| Symbol | IL5 |
| NCBI Gene ID | 3569 |
| Chromosome | 5q31.1 |
| Protein Class | Th2 cytokine |
| Molecular Weight | ~15 kDa (homodimer) |
IL-5 has specialized functions in eosinophil biology:
IL-5 signals through a unique receptor complex:
The γ chain is shared with IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21 receptors.
IL-5 activates specific signaling cascades[4][5]:
The IL-5R consists of two subunits[4:1]:
The γ chain is shared with IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21 receptors.
IL-5 is increasingly recognized in neuroinflammatory conditions[11][12]:
IL-5 expression is primarily in activated immune cells:
| Cell Type | Expression Level | Notes |
|---|---|---|
| Th2 cells | High | Activated CD4+ Th2 cells |
| Eosinophils | Moderate | Autocrine signaling |
| Basophils | Moderate | Activated basophils |
| Mast cells | Moderate | Some subsets |
| Neurons | Low | Limited data |
| Astrocytes | Low | Inducible |
IL-5 pathway is a proven therapeutic target[13][14]:
The IL-5 targeted therapies work through distinct mechanisms:
| Therapy | Mechanism | Administration |
|---|---|---|
| Mepolizumab | Neutralizing IL-5 antibody | Subcutaneous |
| Reslizumab | IL-5 blockade | Intravenous |
| Benralizumab | IL-5Rα depletion | Subcutaneous |
These therapies are being explored for:
Recent research has revealed unexpected roles for eosinophils in CNS homeostasis and disease[16][17].
Eosinophils release various molecules affecting neural function:
Odemuyiwa et al. IL-5 in CNS (2014). 2014. ↩︎
Lee et al. IL-5 and eosinophil development (2010). 2010. ↩︎
Martin et al. IL-5 receptor structure and signaling. 1996. ↩︎ ↩︎
Takatsu et al. IL-5 and eosinophil biology: understanding pathogenesis. 2008. ↩︎
Swanberg et al. IL-5 in multiple sclerosis (2005). 2005. ↩︎
Elsasser et al. IL-5 in neuroinflammation. 2012. ↩︎
Menzies et al. IL-5 and type 2 inflammation in CNS. 2021. ↩︎
Simpson et al. Eosinophil infiltration in AD brain. 2018. ↩︎
Rehman et al. IL-5 and PD neuroinflammation. 2019. ↩︎
Butovsky et al. Microglia and IL-5 in neurodegeneration. 2014. ↩︎
Prinz et al. Neuroinflammation and glial responses. 2011. ↩︎
Nordkild et al. IL-5 as a therapeutic target. 2016. ↩︎
Yang et al. Targeting IL-5 in eosinophilic disorders. 2021. ↩︎
Pavord et al. Mepolizumab for severe eosinophilic asthma (2012). 2012. ↩︎
Cait et al. Eosinophils and brain homeostasis. 2022. ↩︎
Correia et al. Eosinophils in neuroinflammation and behavior. 2022. ↩︎