Possible different serum IL-4 levels across populations: a reason for dissimilar incidence of Th1 and Th2 diseases.

The incidence of a number of Th1 and Th2 diseases differs across populations. Interleukin-4 (IL-4) is a dispensable cytokine for the development of a type 2 immune response. Studies in which serum IL-4 levels were quantified in a healthy control group from some European and Asian countries propose that serum IL-4 levels may be higher in Asian compared to European countries. A simultaneous measurement of serum IL-4 levels in healthy individuals from different populations in a reference lab is needed to confirm different IL-4 levels across populations. If so, increased IL-4 levels might be an explanation for dissimilar incidence of some Th1 and Th2 diseases in different courtiers.