B and T lymphocyte associated (BTLA) is an Ig domain superfamily protein with cytoplasmic immunoreceptor tyrosine-based inhibitory motifs. The herpes virus entry mediator (HVEM), a member of the TNF receptor (TNFR) superfamily, can act as a molecular switch that modulates T cell activation by propagating positive signals from the TNF-related ligand LIGHT (TNFR superfamily 14), or inhibitory signals through the Ig superfamily member BTLA. The binding site on HVEM for BTLA is conserved in the orphan TNF receptor UL144, present in human CMV. UL144 binds BTLA, but not LIGHT, and inhibits T cell proliferation, selectively mimicking the inhibitory cosignaling function of HVEM.
Immunohistochemistry: (frozen sections).