• Purity

  >95%, by SDS-PAGE visualized with Silver Staining and quantitative densitometry by Coomassie® Blue Staining

• Endotoxin Level

  <1.0 EU per 1 μg of the protein by the LAL method.  

• Activity

  Measured by its ability to inhibit anti-CD3 antibody induced IL-2 secretion in human T lymphocytes. The ED    ₅₀ for this effect is 0.5‑2.5 μg/mL.

• Source

  Mouse myeloma cell line, NS0-derived Phe29-Ala258, with a C-terminal 10-His tag

• Accession #

• N-terminal Sequence    
  Analysis

  Phe29

• Predicted Molecular Mass

  26.7 kDa

• SDS-PAGE

  45-60 kDa, reducing conditions

Background: B7-H4

B7-H4, also known as VTCN1, B7x and B7S1, is a 50 ‑ 80 kDa glycosylated member of the BTN/MOG family of immunomodulatory protein (1, 2). Mature human B7-H4 consists of a 235 amino acid (aa) extracellular domain (ECD) with one Ig-like V-set domain and one Ig-like C2-set domain, a 21 aa transmembrane segment, and a 2 aa cytoplasmic tail (3 - 5). Within the ECD, human B7-H4 shares 90% aa sequence identity with mouse and rat B7-H4. It shares 22% - 28% aa sequence identity with human B7-1, B7-2, B7-H1, B7-H2, B7-H3, and PD‑L2. Alternate splicing of human B7-H4 generates an additional isoform that lacks the first Ig-like domain. B7-H4 is expressed on the surface of activated lymphocytes, macrophages, monocytes, dendritic cells, epithelial cells, and bone marrow-derived mesenchymal stem cells (4 - 8). Following binding to activated T cells, B7-H4 serves as a co‑inhibitor of the T cell response. This is accomplished by reverse signaling that can induce either cell cycle arrest, or apoptosis in B7-H4 expressing cells (3 - 5, 9, 10). B7‑H4 is up‑regulated in several carcinomas in correlation with tumor progression and metastasis (2, 7, 11, 12). A soluble form of B7-H4 is elevated in the serum of ovarian cancer, renal cell carcinoma, and rheumatoid arthritis patients, also in correlation with advanced disease status (13 - 15). Soluble B7‑H4 functions as a decoy molecule that blocks the inhibitory influence of B7‑H4 on immune activation (15). Despite evidence for the involvement of B7-H4 in immune regulation, mice deficient in its expression do not show significant immune deficiencies, suggesting compensation by other molecules   in vivo (16).

• References:

1. Yi, K.H. and L. Chen (2009) Immunol. Rev. 229:145.

2. Salceda, S. et al. (2005) Exp. Cell Res. 306:128.

3. Zang, X. et al. (2003) Proc. Natl. Acad. Sci. 100:10388.

4. Prasad, V.R. et al. (2003) Immunity 18:863.

5. Sica, G.L. et al. (2003) Immunity 18:849.

6. Kryczek, I. et al. (2006) J. Exp. Med. 203:871.

7. Tringler, B. et al. (2005) Clin. Cancer Res. 11:1842.

8. Xue, Q. et al. (2010) Stem Cells Dev. 19:27.

9. Song, H. et al. (2008) Cancer Lett. 266:227.

10. Park, G.B. et al. (2009) Immunology 128:360.

11. Zang, X. et al. (2007) Proc. Natl. Acad. Sci. 104:19458.

12. Krambeck, A.E. et al. (2006) Proc. Natl. Acad. Sci. 103:10391.

13. Simon, I. et al. (2006) Cancer Res. 66:1570.

14. Thompson, R.H. et al. (2008) Cancer Res. 68:6054.

15. Azuma, T. et al. (2009) PloS Med. 6:e1000166.

16. Suh, W.-K. et al. (2006) Mol. Cell. Biol. 26:6403.

• Long Name:

  B7 Homolog 4

• Entrez Gene IDs:

  79679 (Human); 242122 (Mouse)

• Alternate Names:

  B7h.5; B7H4; B7-H4; B7H4T-cell costimulatory molecule B7x; B7S1; B7S1VCTN1; B7x; B7XPRO1291; FLJ22418; Immune costimulatory protein B7-H4; Protein B7S1; T cell costimulatory molecule B7x; V-set domain containing T cell activation inhibitor 1; V-set domain-containing T-cell activation inhibitor 1; Vtcn1