Human Blood Basophils Produce Interleukin-l3 in Response to IgE-Receptor-Dependent and -Independent Activation

Interleukin-l3 (IL-13) is a recently discovered immunoregulatory cytokine. The cellular sources of IL-13 and the regulation of its expression are largely unknown. Here we show that human basophils produce IL-13 in response to IgE-receptor (IgER) crosslinking, IL-3, IL-3 plus C5a. but not C5a alone. Human basophils express IL-13 in a restricted manner since, apart from IL-4, no other cytokines encoded on the cytokine gene cluster (IL-3, IL-5, and granulocyte macrophage-colonystimulating factor [GM-CSFI), are induced. Highest levels of IL-13 are formed after IgE-independent activation leading to a prolonged secretion of IL-13. The response to IgER-crosslinking is more transient preferentially inducing IL-4. IL-3 is