Interleukin-4 (IL-4) is a pleiotropic cytokine that regulates diverse T and B cell responses including differentiation of naive T cells into the TH2 phenotype, promoting B cell proliferation, antibody isotype switching, and expression of other TH2 cytokines including IL-5 and IL-9.1,2 IL-4 plays a critical role in the development of allergic inflammation and asthma.3
IL-4 binds to two distinct receptors; the type I receptor, a heterodimer consisting of the IL-4Rα chain and the common gamma chain, γc, and the type II receptor, a heterodimer of IL-4Rα and IL-13Rα1.4
Naturally occurring IL-4 has a molecular mass of 12-20 kDa. Recombinant human IL-4 is a 14.9 kDa protein containing 129 amino acid residues. Human and mouse IL-4 share a 50% amino acid sequence homology, but their biological actions are species-specific.5
1. Paul, W.E., Interleukin-4: a prototypic immuno-regulatory lymphokine. Blood, 77, 1859-1870 (1991).
2. O′Garra, A., and Arai, N., The molecular basis of T helper 1 and T helper 2 cell differentiation. Trends Cell Biol., 10, 542-550 (2000).
3. Ryan, J.J. et al., Mast cell homeostasis: a fundamental aspect of allergic disease. Crit. Rev. Immunol., 27, 15-32 (2007).
4. Callard, R.E. et al., IL-4 and IL-13 receptors: are they one and the same? Immunol. Today, 17, 108-110 (1996).
5. Yokota, T. et al., Molecular biology of interleukin 4 and interleukin 5 genes and biology of their products that stimulate B cells, T cells and hemopoietic cells. Immunol. Rev., 102, 137-187 (1988).
6. Kitamura, T. et al., Establishment and characterization of a unique human cell line that proliferates dependently on GM-CSF, IL-3, or erythropoietin. J. Cell Physiol., 140, 323-334 (1989).