Recombinant Human IL-35 Fc Chimera Protein, CF

Interleukin 35 (IL-35) is a member of the IL-12 family of heterodimeric cytokines. Unlike other IL-12 family cytokines which stimulate the immune response, the predominant function of IL-35 is as an immunosuppressant. IL-12 cytokines are composed of an alpha and beta subunit which, for IL-35 are the IL-12 p35 subunit and the EBI3 subunit, respectively (1-3). The IL-12 p35 subunit of IL-35 is synthesized as a 219 amino acid (aa) precursor protein with a 22 aa signal sequence and a 197 aa mature region. The EBI3 subunit of IL-35 is synthesized as a 229 aa precursor protein that contains a 20 aa signal sequence and a 209 aa mature region. Human and mouse IL-35 share 58% and 62% sequence homology in their IL-12 p35 and EBI3 subunits, respectively. IL-35 binds to the homodimeric receptors, IL-12 R beta2 and gp130, as well as to the IL-12 R beta2-gp130 receptor heterodimer (4). The expression pattern of IL-35 is thought to differ between mouse and humans (5). In mouse regulatory T cells, both subunits of IL-35 are constitutively expressed and the mature IL-35 is secreted. In humans, IL-12 p35 is the only subunit constitutively expressed in regulatory T cells. Immune activation can induce EBI3 expression and IL-35 secretion in human effector T cells (6-8). IL-35 is also expressed and secreted in human placental trophoblasts (1, 9). In both human and mouse IL-35 has been shown to suppress effector T cell proliferation, inhibit Th17 cell development, and promote the conversion of T cells and B cells into regulatory T and B cells, respectively (1, 4, 8, 10, 11). IL-35 is thought to be involved in infectious tolerance and inflammatory cytokine-mediated autoimmune disorders (1, 3, 5, 12). Serum levels of IL-35 are associated with acute graft-versus-host disease following hematopoietic stem cell transplantation (13, 14). IL-35 also functions as a regulator of tumor growth (2, 12, 15).