To  detect   the expression of B and T lymphocyte attenuator (BTLA) antigen in synovial tissues from rheumatoid arthritis (RA) patients.
The expression and distribution of BTLA antigen was analyzed by immunohistochemistry. Moreover,  fluorescence double-staining was  used to  further  identify  the cell types  expressing  BTLA.
Immunohistochemical analysis revealed that a great deal of   BTLA positive cells were found in RA synovium,  and fluorescence double-staining further demonstrated that BTLA positive cells were CD3(+); T cells,  CD68(+); macrophages,  and occasionally   CD31(+); endothelial cells. In contrast to other members of B7 superfamily,  the expression of BTLA was also found on B7-H1(+);,  B7-H4(+); and  HVEM(+); cells,  while it was absence on B7-DC(+); cells as well as B7-H3(+); cells.
The expression of BTLA has been  observed on the surface of several kinds of cells   within synovial tissues of RA patients,  which indicates  this signal might be involved in the regulation of   local T cell activation and  the pathogenesis of RA.