• TREM1 is a myeloid cell surface receptor that is expressed on the surface of neutrophils, monocytes, macrophages, and in various tumor microenvironments, serving as an "amplifier" of inflammatory responses. The extracellular segment of this receptor is cleaved by integrin metalloproteinases, releasing soluble TREM-1 (sTREM-1), which participates in the immune and inflammatory response processes.
• PGLYRP1 is an important effector molecule of the innate immune system that specifically recognizes peptidoglycan components in bacterial cell walls, thereby activating immune responses.
• The genome of the mouse Trem1 gene encoding the extracellular domain was replaced with human TREM1 counterpart in B-hTREM1/hPGLYRP1 mice. The genome of the mouse Pglyrp1 gene encoding the full-length protein was replaced with human PGLYRP1 counterpart in B-hTREM1/hPGLYRP1 mice.
• Human TREM1 and PGLYRP1 protein were only detectable in homozygous B-hTREM1/hPGLYRP1 mice.
• Human TREM1 can be efficiently activated and cleaved in B-hTREM1/hPGLYRP1 mice.
• This product is used for the evaluation of the pharmacodynamics and safety of anti-human TREM1/PGLYRP1 antibodies.

Gene targeting strategy for B-hTREM1/hPGLYRP1 mice.

The exons 1-4 of mouse Trem1 gene that encode signal peptide and extracellular domain are replaced by human counterparts in B-hTREM1/hPGLYRP1 mice. The genomic region of mouse Trem1 gene that encodes transmembrane domain and cytoplasmic portion is retained. The promoter, 5’UTR and 3’UTR region of the mouse gene are also retained. The chimeric TREM1 expression is driven by endogenous mouse Trem1 promoter, while mouse Trem1 gene transcription and translation will be disrupted.

The exons 1-3 of mouse Pglyrp1 gene that encode the whole molecule (ATG to STOP codon), including 3’UTR were replaced by human counterparts in B-hTREM1/hPGLYRP1 mice. The promoter and 5’UTR region of the mouse gene are retained. The human PGLYRP1 expression is driven by endogenous mouse Pglyrp1 promoter, while mouse Pglyrp1 gene transcription and translation will be disrupted.

Strain specific TREM1 expression analysis in homozygous B-hTREM1/hPGLYRP1 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6 mice (+/+) and homozygous B-hTREM1/hPGLYRP1 mice (H/H;H/H), and analyzed by flow cytometry with species-specific anti-mouse TREM1 antibody (Mouse TREM-1 PE-conjugated Antibody, R&D, FAB1187P) and anti-human TREM1 antibody (APC anti-human CD354 (TREM-1) Antibody, Biolegend, 314909). Mouse TREM1 was only detectable in neutrophils of wild-type C57BL/6 mice. Human TREM1 was exclusively detectable in neutrophils of homozygous B-hTREM1/hPGLYRP1 mice but not in wild-type mice.

Strain specific TREM1 expression analysis in homozygous B-hTREM1/hPGLYRP1 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6 mice (+/+) and homozygous B-hTREM1/hPGLYRP1 mice (H/H;H/H), and analyzed by flow cytometry with species-specific anti-mouse TREM1 antibody (Mouse TREM-1 PE-conjugated Antibody, R&D, FAB1187P) and anti-human TREM1 antibody (APC anti-human CD354 (TREM-1) Antibody, Biolegend, 314909). Mouse TREM1 was only detectable in CD11b+ cells of wild-type C57BL/6 mice. Human TREM1 was exclusively detectable in CD11b+ cells of homozygous B-hTREM1/hPGLYRP1 mice but not in wild-type mice.

Strain specific TREM1 expression analysis in wild-type C57BL/6 mice and homozygous humanized B-hTREM1/hPGLYRP1 mice by ELISA. Serum was collected from wild-type C57BL/6 (+/+) (female, n=3, 6-week-old) and homozygous B-hTREM1/hPGLYRP1 mice (H/H;H/H) (female, n=3, 6-week-old) stimulated with 20 μg/mouse LPS in vivo for 2 hrs. Expression level of mouse and human TREM1 were analyzed by ELISA (anti-mouse TREM1 ELISA kit: R&D, MTRM10; anti-human TREM1 ELISA kit: R&D, DTRM10C). Mouse TREM1 was only detectable in wild-type C57BL/6 mice. Human TREM1 was exclusively detectable in homozygous B-hTREM1/hPGLYRP1 mice (n=3), which indicating that mouse matrix metalloproteinase(MMP) was capable of proteolytically cleaving human TREM1, and inducing the release of soluble TREM1. Values are expressed as mean ± SEM.

Strain specific PGLYRP1 expression analysis in wild-type C57BL/6 mice and homozygous humanized B-hTREM1/hPGLYRP1 mice by ELISA. Serum was collected from wild-type C57BL/6 (+/+) (female, n=3, 6-week-old) and homozygous B-hTREM1/hPGLYRP1 mice (H/H;H/H) (female, n=3, 6-week-old) stimulated with or without LPS in vivo for 2 hrs. Expression level of mouse and human PGLYRP1 were analyzed by ELISA (anti-mouse PGLYRP1 ELISA kit: OriGene, EA102442; anti-human TREM1 ELISA kit: R&D, DY2590). Mouse PGLYRP1 was only detectable in wild-type C57BL/6 mice. Human PGLYRP1 was exclusively detectable in homozygous B-hTREM1/hPGLYRP1 mice. Values are expressed as mean ± SEM.