Epstein-Barr virus induced gene 3 was identified by the induction of its expression in B lymphocytes by Epstein-Barr virus infection. The protein encoded by this gene is a secreted glycoprotein, which is a member of the hematopoietin receptor family related to the p40 subunit of interleukin 12 (IL-12). It plays a role in regulating cell-mediated immune responses.EBI3 is a subunit in 2 distinct heterodimeric cytokines: interleukin-27 (IL27) and IL35.

IL27 is composed of p28 (IL27) and EBI3. IL27 can trigger signaling in T cells, B cells, and myeloid cells. IL35, an inhibitory cytokine involved in regulatory T-cell function, is composed of EBI3 and the p35 subunit of IL12.Interleukin-27 (IL-27) is composed of two subunits, Epstein-Barr virus (EBV)-induced gene 3 (EBI3) (IL-27B) and IL27-p28 (known as IL-30).