TL1A: A key inflammation cytokine in chronic intestinal inflammation and fibrosis-related diseases 

• Gene Information: TNF Superfamily Member 15 (TNFSF15, also known as TL1A) is a protein-coding gene located on chromosome 9q32. This cytokine is a ligand for receptor TNFRSF25 (also known as DR3) and TNFRSF6B (also known as DcR3). 
• Protein Expression: TL1A is expressed in various immune cells (such as monocytes, macrophages, dendritic cells, and T cells) as well as in non-immune cells (such as synovial fibroblasts and endothelial cells). TL1A is a type II transmembrane protein that exists in either membrane-bound (mTL1A) or soluble (sTL1A) forms. 
• Signaling Pathway: TL1A competes with Death Receptor 3 (DR3) for binding, providing stimulus signals for downstream signaling pathways, thereby regulating the proliferation, activation, apoptosis of effector cells, and the production of cytokines and chemokines. 
• Therapeutic Inhibition: Blocking the interaction between TL1A and DR3 can reduce the severity of autoimmune diseases, such as the inflammatory bowel disease (IBD) model.

• Gene Information: Integrin α4β7 is composed of a 150 kD (α4 or CD49d) and a 130 kD (β7) heterodimer, also known as CD49d/β7 or LPAM-1. ITGA4 is located on chromosome 2q31.3, ITGB7 is located on chromosome 12q13.13. Integrin α4β7 binds its ligand MAdCAM-1, and plays an important role in lymphocytes adhesion. 
• Protein Expression: The α4β7 integrin is a heterodimer, composed of an α4 subunit and a β7 subunit. α4β7 is mainly expressed in leukocytes, such as T cells, B cells, NK cells, macrophages, dendritic cells, monocytes, and others. 
• Signaling Pathway: Integrin α4β7 interacts with the cell surface adhesion molecules MAdCAM-1 which is normally expressed by the vascular endothelium of the gastrointestinal tract, which is a central pathway for directing lymphocyte migration to the gut and other mucosal sites during inflammation. 
• Therapeutic Inhibition: Blocking the binding of α4β7 to MAdCAM-1, such as with Vedolizumab, inhibits lymphocyte homing and infiltration into inflammatory tissues such as the intestine.

TL1A 

• The targeting strategy for humanized TL1A in B-hTL1A plus/hα4β7 mice is currently kept confidential.

ITGA4

•  The exons 1-27 of mouse Itga4 gene that encode the extracellular domain were replaced by human counterparts in B-hTL1A plus/hα4β7 mice. 
• The promoter, 5’UTR and 3’UTR region of the mouse gene were retained. The human ITGA4 expression was driven by endogenous mouse Itga4 promoter, while mouse Itga4 gene transcription and translation will be disrupted.

ITGB7 

• The exons 2-14 of mouse Itgb7 gene that encode the extracellular domain were replaced by human counterparts in B-hTL1A plus/hα4β7 mice.
• The promoter, 5’UTR and 3’UTR region of the mouse gene were retained. The human ITGB7 expression was driven by endogenous mouse Itgb7 promoter, while mouse Itgb7 gene transcription and translation will be disrupted. 

B-hTL1A plus/hα4β7 mice were obtained by mating B-hTL1A mice plus (112949) and B-hα4β7 mice (111913).

Soluble TL1A expression analysis in B-hTL1A plus/hα4β7 mice by ELISA. Bone marrow derived dendritic cells (BMDC) were produced by culturing the bone marrow from wild-type C57BL/6JNifdc mice (+/+), homozygous B-hTL1A/hα4β7 mice (H/H;H/H;H/H) and B-hTL1A plus/hα4β7 mice (H/H;H/H;H/H), which were stimulated with LPS in vitro. After stimulation, the supernatants were collected and the level of soluble TL1A was analyzed by ELISA. Soluble human TL1A was exclusively detectable in homozygous B-hTL1A/hα4β7 mice and B-hTL1A plus/hα4β7 mice, but not in wild-type C57BL/6JNifdc mice. Values are expressed as mean ± SEM. ND: not detectable.

Strain specific ITGA4 and ITGB7 expression analysis in wild-type C57BL/6JNifdc mice and homozygous humanized B-hTL1A plus/hα4β7 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hTL1A plus/hα4β7 mice (H/H;H/H;H/H). Protein expression was analyzed with anti-mouse ITGA4 antibody (Biolegend, 103705), anti-mouse LPAM-1/α4β7 antibody (Biolegend, 120607), anti-human ITGA4 antibody (Biolegend, 304307) anti-human ITGB7 antibody (Invitrogen, MA5-23541) by flow cytometry. Mouse ITGA4 and ITGB7 were only detectable in wild-type C57BL/6JNifdc mice. Human ITGA4 and ITGB7 were exclusively detectable in homozygous B-hTL1A plus/hα4β7 mice, but not in wild-type C57BL/6JNifdc mice.

Strain specific ITGA4 and ITGB7 expression analysis in wild-type C57BL/6JNifdc mice and homozygous humanized B-hTL1A plus/hα4β7 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hTL1A plus/hα4β7 mice (H/H;H/H;H/H). Protein expression was analyzed with anti-mouse ITGA4 antibody (Biolegend, 103705), anti-mouse LPAM-1/α4β7 antibody (Biolegend, 120607), anti-human ITGA4 antibody (Biolegend, 304307) anti-human ITGB7 antibody (Invitrogen, MA5-23541) by flow cytometry. Mouse ITGA4 and ITGB7 were only detectable in wild-type C57BL/6JNifdc mice. Human ITGA4 and ITGB7 were exclusively detectable in homozygous B-hTL1A plus/hα4β7 mice, but not in wild-type C57BL/6JNifdc mice.

Strain specific ITGA4 and ITGB7 expression analysis in wild-type C57BL/6JNifdc mice and homozygous humanized B-hTL1A plus/hα4β7 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hTL1A plus/hα4β7 mice (H/H;H/H;H/H). Protein expression was analyzed with anti-mouse ITGA4 antibody (Biolegend, 103705), anti-mouse LPAM-1/α4β7 antibody (Biolegend, 120607), anti-human ITGA4 antibody (Biolegend, 304307) anti-human ITGB7 antibody (Invitrogen, MA5-23541) by flow cytometry. Mouse ITGA4 and ITGB7 were only detectable in wild-type C57BL/6JNifdc mice. Human ITGA4 and ITGB7 were exclusively detectable in homozygous B-hTL1A plus/hα4β7 mice, but not in wild-type C57BL/6JNifdc mice.

Strain specific ITGA4 and ITGB7 expression analysis in wild-type C57BL/6JNifdc mice and homozygous humanized B-hTL1A plus/hα4β7 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hTL1A plus/hα4β7 mice (H/H;H/H;H/H). Protein expression was analyzed with anti-mouse ITGA4 antibody (Biolegend, 103705), anti-mouse LPAM-1/α4β7 antibody (Biolegend, 120607), anti-human ITGA4 antibody (Biolegend, 304307) anti-human ITGB7 antibody (Invitrogen, MA5-23541) by flow cytometry. Mouse ITGA4 and ITGB7 were only detectable in wild-type C57BL/6JNifdc mice. Human ITGA4 and ITGB7 were exclusively detectable in homozygous B-hTL1A plus/hα4β7 mice, but not in wild-type C57BL/6JNifdc mice.

Strain specific ITGA4 and ITGB7 expression analysis in wild-type C57BL/6JNifdc mice and homozygous humanized B-hTL1A plus/hα4β7 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hTL1A plus/hα4β7 mice (H/H;H/H;H/H). Protein expression was analyzed with anti-mouse ITGA4 antibody (Biolegend, 103705), anti-mouse LPAM-1/α4β7 antibody (Biolegend, 120607), anti-human ITGA4 antibody (Biolegend, 304307) anti-human ITGB7 antibody (Invitrogen, MA5-23541) by flow cytometry. Mouse ITGA4 and ITGB7 were only detectable in wild-type C57BL/6JNifdc mice. Human ITGA4 and ITGB7 were exclusively detectable in homozygous B-hTL1A plus/hα4β7 mice, but not in wild-type C57BL/6JNifdc mice.

Strain specific ITGA4 and ITGB7 expression analysis in wild-type C57BL/6JNifdc mice and homozygous humanized B-hTL1A plus/hα4β7 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hTL1A plus/hα4β7 mice (H/H;H/H;H/H). Protein expression was analyzed with anti-mouse ITGA4 antibody (Biolegend, 103705), anti-mouse LPAM-1/α4β7 antibody (Biolegend, 120607), anti-human ITGA4 antibody (Biolegend, 304307) anti-human ITGB7 antibody (Invitrogen, MA5-23541) by flow cytometry. Mouse ITGA4 and ITGB7 were only detectable in wild-type C57BL/6JNifdc mice. Human ITGA4 and ITGB7 were exclusively detectable in homozygous B-hTL1A plus/hα4β7 mice, but not in wild-type C57BL/6JNifdc mice.