• Fc Receptor-Like 1 (FCRL1), also known as FcRH1, and IRTA5, is an approximately 50 kDa protein with sequence homology to classical Fc receptors, which consists of a 291 amino acid (aa) extracellular domain (ECD) with three Ig-like domains, a 21 aa transmembrane segment, and a 101 aa cytoplasmic domain with two immunotyrosine activation motifs (ITIMs).
• The exons 1-6 of mouse Fcrl1 gene that encode signal peptide, extracellular domain are replaced by human counterparts in B-hFCRL1 mice. The promoter, 5’UTR, transmembrane domain, cytoplasmic region and 3’UTR region of the mouse gene are retained. The human FCRL1 expression is driven by endogenous mouse Fcrl1 promoter, while mouse Fcrl1 gene transcription and translation will be disrupted. 
• Mouse FCRL1 was detectable on T cells, B cells, NK cells, monocytes, macrophages, DCs and neutrophils from spleen of wild-type C57BL/6JNifdc mice, especially, which is highly expressed in B cells.
• Mouse FCRL1 was detectable on T cells, B cells, NK cells, monocytes, macrophages, DCs and neutrophils from blood of wild-type C57BL/6JNifdc mice, especially, which is highly expressed in B cells.
• Mouse FCRL1 was detectable on T cells, B cells and NK cells from lymph nodes of wild-type C57BL/6JNifdc mice, especially, which is highly expressed in B cells.
• Human FCRL1 was detectable on B cells, NK cells, monocytes, macrophages, DCs and neutrophils from spleen of B-hFCRL1 mice, especially, which is highly expressed in B cells.
• Human FCRL1 was detectable on B cells, NK cells, monocytes, macrophages, DCs and neutrophils from blood of B-hFCRL1 mice, especially, which is highly expressed in B cells.
• Human FCRL1 was detectable on B cells and NK cells from lymph nodes of B-hFCRL1 mice, especially, which is highly expressed in B cells.
• Application: This product is used for pharmacodynamics and safety evaluation of autoimmunity drugs.

Gene targeting strategy for B-hFCRL1 mice. The exons 1-6 of mouse Fcrl1 gene that encode signal peptide, extracellular domain are replaced by human counterparts in B-hFCRL1 mice. The promoter, 5’UTR, transmembrane domain, cytoplasmic region and 3’UTR region of the mouse gene are retained. The human FCRL1 expression is driven by endogenous mouse Fcrl1 promoter, while mouse Fcrl1 gene transcription and translation will be disrupted. 

Strain specific FCRL1 expression analysis in homozygous B-hFCRL1 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hFCRL1 mice (H/H), and protein expression was analyzed with anti-mouse FCRL1 antibody (Miltenyi, 130-108-752)  and anti-human FCRL1 antibody (BD, 566457) by flow cytometry. mFCRL1 was detectable in T cells, B cells(high expression) and NK cells of wild-type C57BL/6JNifdc mice. hFCRL1 was detectable in B cells(high expression) and NK cells of homozygous B-hFCRL1 mice. 

Strain specific FCRL1 expression analysis in homozygous B-hFCRL1 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hFCRL1 mice (H/H), and protein expression was analyzed with anti-mouse FCRL1 antibody (Miltenyi, 130-108-752)  and anti-human FCRL1 antibody (BD, 566457) by flow cytometry. mFCRL1 was detectable in monocytes and macrophages of wild-type C57BL/6JNifdc mice. hFCRL1 was detectable in monocytes and macrophages of homozygous B-hFCRL1 mice. 

Strain specific FCRL1 expression analysis in homozygous B-hFCRL1 mice by flow cytometry. Splenocytes were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hFCRL1 mice (H/H), and protein expression was analyzed with anti-mouse FCRL1 antibody (Miltenyi, 130-108-752)  and anti-human FCRL1 antibody (BD, 566457) by flow cytometry. mFCRL1 was detectable in DCs and neutrophils of wild-type C57BL/6JNifdc mice. hFCRL1 was detectable in DCs and neutrophils of homozygous B-hFCRL1 mice. 

Strain specific FCRL1 expression analysis in homozygous B-hFCRL1 mice by flow cytometry. Blood cells were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hFCRL1 mice (H/H), and protein expression was analyzed with anti-mouse FCRL1 antibody (Miltenyi, 130-108-752)  and anti-human FCRL1 antibody (BD, 566457) by flow cytometry. mFCRL1 was detectable in T cells, B cells(high expression) and NK cells of wild-type C57BL/6JNifdc mice. hFCRL1 was detectable in B cells(high expression) and NK cells of homozygous B-hFCRL1 mice. 

Strain specific FCRL1 expression analysis in homozygous B-hFCRL1 mice by flow cytometry. Blood cells were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hFCRL1 mice (H/H), and protein expression was analyzed with anti-mouse FCRL1 antibody (Miltenyi, 130-108-752)  and anti-human FCRL1 antibody (BD, 566457) by flow cytometry. mFCRL1 was detectable in monocytes and macrophages of wild-type C57BL/6JNifdc mice. hFCRL1 was detectable in monocytes and macrophages of homozygous B-hFCRL1 mice. 

Strain specific FCRL1 expression analysis in homozygous B-hFCRL1 mice by flow cytometry. Blood cells were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hFCRL1 mice (H/H), and protein expression was analyzed with anti-mouse FCRL1 antibody (Miltenyi, 130-108-752)  and anti-human FCRL1 antibody (BD, 566457) by flow cytometry. mFCRL1 was detectable in DCs and neutrophils of wild-type C57BL/6JNifdc mice. hFCRL1 was detectable in DCs and neutrophils of homozygous B-hFCRL1 mice. 

Strain specific FCRL1 expression analysis in homozygous B-hFCRL1 mice by flow cytometry. lymph nodes were collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hFCRL1 mice (H/H), and protein expression was analyzed with anti-mouse FCRL1 antibody (Miltenyi, 130-108-752)  and anti-human FCRL1 antibody (BD, 566457) by flow cytometry. mFCRL1 was detectable in T cells, B cells(high expression) and NK cells of wild-type C57BL/6JNifdc mice. hFCRL1 was detectable in B cells(high expression) and NK cells of homozygous B-hFCRL1 mice.