• TL1A is a type II transmembrane protein that exists in either membrane-bound (mTL1A) or soluble (sTL1A) forms. 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 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.
• TL1A can independently mediate inflammation and fibrosis, and is linked to the occurrence and pathogenesis of diseases such as rheumatoid arthritis (RA), atopic dermatitis, systemic lupus erythematosus, asthma, and psoriasis. The TL1A/DR3 pathway is a crucial component of mucosal immunity and intestinal homeostasis, and its clinical significance has been validated for the treatment of inflammatory bowel disease (IBD).
• The genome of mouse Tl1a encoding the extracellular domain was replaced by human counterparts in B-hTL1A mice. 
• Human TL1A protein and RNA were detectable in homozygous B-hTL1A mice. Humanization of TL1A does not change the overall frequency or distribution of immune cell types in spleen, blood, and lymph nodes. In TNBS-induced acute colitis and DSS-induced acute colitis in B-hTL1A mice, treatment with the anti-human TL1A antibody improved the disease characteristics of colitis.
• This product is used for the evaluation of the pharmacodynamics and safety of anti-human TL1A antibodies in autoimmune diseases such as inflammatory bowel disease.

Gene targeting strategy for B-hTL1A mice. The exons 1-14 of mouse Tl1a gene that encode extracellular domain were replaced by human counterparts in B-hTL1A mice. The genomic region of mouse Tl1a gene that encodes transmembrane domain and cytoplasmic portion was retained. The promoter, 5’UTR and 3’UTR region of the mouse gene were also retained. The chimeric TL1A expression was driven by endogenous mouse Tl1a promoter, while mouse Tl1a gene transcription and translation will be disrupted. 

Strain specific analysis of TL1A gene expression in wild-type (WT) mice and B-hTL1A mice by RT-PCR. Mouse Tl1a mRNA was detectable only in lung and colon of wild-type C57BL/6 mice (+/+). Human TL1A mRNA was detectable only in homozygous B-hTL1A mice (H/H) but not in wild-type C57BL/6 mice (+/+) . 

Strain specific TL1A expression analysis in wild-type C57BL/6 mice and homozygous humanized B-hTL1A mice by flow cytometry. Lung endothelial cells were collected from wild-type C57BL/6 mice (+/+) and homozygous B-hTL1A mice (H/H). Protein expression was analyzed with anti-TL1A antibody by flow cytometry. TL1A was detectable in wild-type C57BL/6 mice and homozygous B-hTL1A mice due to the cross-reactivity of antibodies. 

Soluble TL1A expression analysis in B-hTL1A mice by ELISA. Bone marrow derived dendritic cells (BMDCs) were produced by culturing the bone marrow from wild-type C57BL/6 mice (+/+) and homozygous B-hTL1A mice (H/H) (male, 6 weeks-old, n=3), which were stimulated with LPS in vitro. After stimulation, the supernatants were collected and the levels of soluble TL1A were measured using a species-specific human TL1A ELISA kit. Soluble human TL1A was exclusively detectable in homozygous B-hTL1A mice but not wild-type C57BL/6 mice. Values are expressed as mean ± SEM. ND: not detectable. 

Frequency of leukocyte subpopulations in spleen by flow cytometry. Splenocytes were isolated from wild-type C57BL/6N mice and homozygous B-hTL1A mice (female, 7-week-old, n=3). A. Flow cytometry analysis of the splenocytes was performed to assess the frequency of leukocyte subpopulations. B. Frequencies of T cell subpopulations. Percentages of T cells, B cells, NK cells, DCs, monocytes, macrophages, neutrophils, CD4+ T cells, CD8+ T cells and Tregs in B-hTL1A mice were similar to those in C57BL/6N mice, demonstrating that humanization of TL1A does not change the frequency or distribution of these cell types in spleen. Values are expressed as mean ± SEM. 

Frequency of leukocyte subpopulations in blood by flow cytometry. Blood cells were isolated from wild-type C57BL/6N mice and homozygous B-hTL1A mice (female, 7-week-old, n=3). A. Flow cytometry analysis of the blood cells was performed to assess the frequency of leukocyte subpopulations. B. Frequencies of T cell subpopulations. Percentages of T cells, B cells, NK cells, DCs, monocytes, macrophages, neutrophils, CD4+ T cells, CD8+ T cells and Tregs in B-hTL1A mice were similar to those in C57BL/6N mice, demonstrating that humanization of TL1A does not change the frequency or distribution of these cell types in blood. Values are expressed as mean ± SEM. 

Frequency of leukocyte subpopulations in lymph nodes by flow cytometry. Leukocytes were isolated from wild-type C57BL/6N mice and homozygous B-hTL1A mice (female, 7-week-old, n=3). A. Flow cytometry analysis of the leukocytes was performed to assess the frequency of leukocyte subpopulations. B. Frequencies of T cell subpopulations. Percentages of T cells, B cells, NK cells, CD4+ T cells, CD8+ T cells and Tregs in B-hTL1A mice were similar to those in C57BL/6N mice, demonstrating that humanization of TL1A does not change the frequency or distribution of these cell types in lymph nodes. Values are expressed as mean ± SEM. 

TNBS solution was instilled into the colon lumen of B-hTL1A mice (female, 8-10 weeks-old, n=8). The control group (Sham) received intrarectal injections of PBS. Tulisokibart (PRA023) at a dose of 25 mpk (provided by WuXi AppTec) was administered to the treatment group. Body weight and DAI score were recorded daily. On day 5, the mice were sacrificed, and colon length and weight were recorded. Colon tissue was later used for H&E staining and Masson staining. (A) Body weight change. (B) DAI score. (C) Colon Index. (D) Pathological score. (E) Masson staining score. An acute colitis disease model induced by TNBS was established in B-hTL1A mice, and the administration of the anti-human TL1A antibody Tulisokibart (PRA023) efficiently improved TNBS-induced acute colitis. The results indicate that B-hTL1A mice are a powerful tool for assessing the in vivo efficacy of anti-human TL1A antibodies. Values are expressed as mean ± SEM. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001 versus Vehicle, ANOVA.

B-hTL1A mice (female, 7-8 weeks-old, n=8) were provided with drinking water containing DSS for 9 consecutive days. Tulisokibart (PRA023) at a dose of 25 mpk (provided by WuXi AppTec) was administered to the treatment group. Body weight changes and clinical scores (weight loss score, stool hardness score, blood in stool score, and total DAI score) were recorded throughout the experiment. On day 8, the mice were sacrificed, and colon length and weight were recorded. (A) Body weight change. (B) DAI score. (C) Colon Index. An acute colitis disease model induced by DSS was established in B-hTL1A mice, and the administration of the anti-human TL1A antibody Tulisokibart (PRA023) improved the clinical symptoms of DSS-induced acute colitis. The results indicate that B-hTL1A mice are a powerful tool for assessing the in vivo efficacy of anti-human TL1A antibodies. Values are expressed as mean ± SEM. *p<0.05, **p<0.01, ***p<0.001, ****p<0.0001 versus Vehicle, ANOVA.