| B- and T-lymphocyte attenuator (BTLA, CD272) is a 70kD, Ig-superfamily, type I transmembrane glycoprotein that is structurally similar to the CD28 family of T cell costimulatory or coinhibitory molecules. (1-3) Unlike CD28 family members, however, the BTLA extracellular Ig domain is an I-type rather than V-type domain, and BTLA does not form homodimers. (4) BTLA also differs from CD28 family members through the interaction of its Ig domain with the TNF superfamily member HVEM (Herpes virus entry mediator, TNFSF14) rather than with B7 family ligands. (5) BTLA is a coinhibitory molecule expressed on T cells, B cells and, depending on the mouse strain, macrophages, dendritic and NK cells. (6) Expression is low in naive T cells and increased during antigen-specific induction of anergy. In B cells, BTLA is highest when cells are mature and naive. (6) BTLA apparently limits T cell numbers, since deletion of BTLA results in overproduction of T cells, especially CD8+ memory T cells that are hyper-responsive to TCR crosslinking. (7) The 305 amino acid (aa) BTLA contains a 29 aa signal sequence, a 153 aa extracellular domain (ECD), a 21 aa transmembrane sequence, and a 102 aa cytoplasmic domain. There are two ITIM motifs and three Tyr phosphorylation sites in the cytoplasmic tail that mediate inhibitory signaling. (8, 9) The binding of the BTLA to HVEM does not preclude additional binding of a mammalian stimulatory HVEM ligand, either LIGHT or lymphotoxin-alpha to the complex. (4) At least three alleles varying by up to ten extracellular amino acids occur in different mouse strains. (6) The ECD of C57BL/6 BTLA shows 51%, 77% and 40% aa identity to that of human, rat and dog BTLA, respectively. A splice variant lacking the Ig domain, termed BTLAs, has been reported. (3) Source: Mouse BTLA (Met 1-Gly 176), IEGRMDP Mouse IgG2a (Glu 98-Lys 330). A DNA sequence encoding the extracellular domain of mouse BTLA (Met 1-Gly 176, Accession AAI08964) with an amino acid variant of Glu 173-Lys 173 was fused to the Fc region of mouse IgG2a via a polypeptide linker. The protein was expressed in a mouse myeloma cell line, NS0. Molecular Mass: Based on N-terminal sequencing, the recombinant protein begins with Glu 30. The recombinant mature monomeric mouse BTLA/Fc chimera has a calculated molecular mass of approximately 44kD. In SDS-PAGE, the recombinant protein migrates as a 60-70kD protein under reducing conditions. Activity: Measured by its ability to bind immobilized rhHVEM/Fc (Gonzalez, LC, et. al., 2005, PNAS 102:1116). Storage: Lyophilized samples are stable for up to twelve months at -20C. Upon reconstitution, this protein, in the presence of a carrier protein, can be stored under sterile conditions at 2-8C for one month or at -20C in a manual defrost freezer for three months without detectable loss of activity. Avoid repeated freeze-thaw cycles. |
