TNFRSF9 (Tumor necrosis factor receptor super family, member 9), also called CD137 and 4-1BB, is a co-stimulatory molecule and is mainly expressed on the surface of T, B, NK and mononuclear cells. CD137 is activated by its ligand CD137L or activating anti-CD137 antibodies enhance tumor rejection because it is upregulated on T cells following activation and its engagement increases T cell proliferation and pro-inflammatory cytokine production.
CD40 (CD40 molecule) also is a member of the tumor necrosis factor receptor superfamily expressed on APC such as dendritic cells (DC), B cells, and monocytes as well as many non-immune cells and a wide range of tumors. Engagement with its trimeric ligand CD154 on activated T helper cells results in APC activation, which has been found to be essential in mediating a broad variety of immune and inflammatory responses including T cell-dependent immunoglobulin class switching, memory B cell development, and germinal center formation. Agonistic CD40 monoclonal antibodies (mAbs) have been shown to activate APC and promote anti-tumor T cell responses. Thus, agonistic anti-CD40 mAb may serve as a new class of antitumor therapeutics that potentiate immunity via a different mechanism than the blocking immune checkpoint inhibitors such as anti-CTLA4 or anti-PD-1.
Gene targeting strategy for B-h4-1BB/hCD40 mice. The exon 2-7 of mouse 4-1bb gene that encodes the extracellular domain was replaced by human 4-1BB counterpart gene in B-h4-1BB/hCD40 mice. The exon 2-7 of mouse Cd40 gene that encodes the extracellular domain was replaced by human CD40 exon 2-7 in B-h4-1BB/hCD40 mice.
Protein expression analysis
Strain specific CD40 and 4-1BB expression analysis in homozygous B-h4-1BB/hCD40 mice by flow cytometry. Splenocytes were collected from wild-type mice (+/+) and homozygous B-h4-1BB/hCD40 mice (H/H) stimulated with anti-CD3ε in vivo (7.5 μg/mice for 24 hours, i.p.), and analyzed by flow cytometry with species-specific anti-CD40 antibody and species-specific anti-4-1BB antibody . Mouse CD40 and 4-1BB were detectable in wild-type mice. Human CD40 and 4-1BB were exclusively detectable in homozygous B-h4-1BB/hCD40 mice (H/H) but not in wild-type mice.
Human CD40 and 4-1BB were exclusively detectable in homozygous B-h4-1BB/hCD40 mice (H/H) but not in wild-type mice.