title: Frontline: Characterization of BT3 molecules belonging to the B7 family expressed on immune cells.
abstract: New members of the B7 family have been recently described as regulators of T cell activation and function. Butyrophilin (BT) has also been related to the B7 family by sequence similarity analyses. We present a new subfamily called BT3, which belongs to the B7/BT family. The BT3 subfamily comprises three members (BT3.1,.2 and.3) that exhibit 95% identity and form a monophylogenetic group along with the BT-related members. High expression levels of BT3 transcripts were detected in lymphoid tissues (mainly spleen, lymph node and PBL). Using anti-BT3 mAb we could demonstrate BT3 expression on immune cells including T, B and NK cells, monocytes and dendritic cells as well as hematopoietic precursors and some tumor cell lines. As described earlier for PDL-1 and ICOS-L, BT3 molecules are expressed on endothelial cells and up-regulated upon activation by IFN-gamma or TNF-alpha. The BT3.1 counter-receptor (BT3.1-R) was analyzed by means of binding experiments using BT3.1-Ig soluble protein. The BT3.1-R is not CD28, CTLA-4, ICOS, PD-1 or BTLA and seems restricted to some T cell and hematopoietic cell lines. Altogether, these data describe new members of the B7/BT family that may play a role in regulation of the immune response.
authors.affiliation: INSERM UMR 599, Université de la Méditerranée, Cancer and Immunology Institute of Marseille, IFR 137, 27 Boulevard Lei Roure, F-13009 Marseille, France.
authors.forename: Elsa
authors.initials: E
authors.lastname: Compte
authors.forename: Pierre
authors.initials: P
authors.lastname: Pontarotti
authors.forename: Yves
authors.initials: Y
authors.lastname: Collette
authors.forename: Marc
authors.initials: M
authors.lastname: Lopez
authors.forename: Daniel
authors.initials: D
authors.lastname: Olive
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018122:B7-1 Antigen / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D016466:CHO Cells; D006224:Cricetinae; D006801:Humans; D008969:Molecular Sequence Data; D005810:Multigene Family; D017434:Protein Structure, Tertiary; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D018122:B7-1 Antigen