Seasonal variation in interleukin 4 in patients with hayfever.

This study was performed to investigate the value of interleukin 4 as a marker of activity in mild atopic disease. We compared IL-4 levels to eosinophil cationic protein (ECP), a suggested inflammatory marker in allergic disease, in patients with hayfever. Patients with hayfever were assessed during January and then in late June at the height of the grass pollen season, and their levels of serum ECP and IL-4 compared. Serum ECP was determined by radio-immunoassay and serum IL-4 by a high-sensitivity enzyme-linked immunosorbent assay. ECP was found to increase significantly in patients with hayfever during the grass pollen season (P<0.01). Conversely, serum levels of IL-4 were found to decrease significantly over the same period when compared with winter values. ECP and IL-4 were not seen to correlate significantly with each other. The fall in serum IL-4 seen during the grass pollen season in the hayfever patients may reflect allergen driven upregulation of membrane IL-4 receptor expression or sequestration of cytokine producing cells to inflammatory sites. These findings suggest that serum IL-4 is a poor indicator of inflammatory status in allergic disease.