Produced predominantly by parasite/allergen activated T-cells, IL-5 is associated mainly with growth and differentiation of B-cells and eosinophils. Naturally, IL-5 is a glycosylated homodimer which binds to a heterodimeric receptor made up of an IL-5 specific alpha subunit and a shared beta subunit. The beta subunit is also used by IL-3 and GM-CSF receptors.

Though IL-5 has effects on B-cells and has bee reported to be a basophile differentiation factor, the effects of IL-5 seem to be more related to eosinophils humans where it is heavily involved in growth, differentiation, survival, and chemotaxis. Because of it’s involvement with eosinophils and mast cells, IL-5 has reportedly been involved in allergenic and asthmatic disease progression.

In summary, under most experimental conditions, IL-5 is rarely observed. However, when eosinophils are involved, IL-5 plays a dramatic and crucial role. IL-5 will often be tested along with other chemotactic proteins in determining eosinophil recruitment and with pro-/anti-inflammatory mediators in chronic diseases.