Interleukin 35 is an immune-suppressive cytokine expressed in stimulated human regulatory Tcells during inflammatory responses and consists of Interlukin-12a ( Interleukin 12p35 subunit) and IL-27b chains, encoded by the Interleukin 12A and Epstien Bar I3 genes, respectively. It is a novel heterodimeric cytokine belonging to the Interleukin 12 family, and little is known about its receptor. Activated peripheral blood mononuclear cell (PBMC)- derived human regulatory T cells have been shown to express and secrete large amounts of Interleukin 35, which contributes significantly to the suppressive capacity of regulatory T cells in an Interlukin 35-dependent manner.