The role of LAIR-1 (CD305) in T cells and monocytes/macrophages in patients with rheumatoid arthritis

• LAIR-1 expression was down-regulated on circulating CD4+ T cells in RA and OA patients.
• LAIR-1 remained high expression on monocytes and synovium macrophages in RA patients.
• TNF-α is the key factor that decreased LAIR-1 expression on CD4+ T cells, especially in Th1 and Th2 subpopulations.

The LAIR-1 receptor is expressed on a majority of mononuclear leukocytes. It is used as a biomarker when testing synovial fluid for evidence of rheumatoid arthritis (RA). The primary objective of this study was to measure T cell- and monocyte/macrophage-specific LAIR-1 expression in RA patients and compare this to LAIR-1 expression in osteoarthritis (OA) patients and healthy individuals. LAIR-1 expression was significantly decreased in circulating CD4+ T cells in RA patients compared to both OA patients and healthy individuals. In contrast, LAIR-1 is high in CD14+ monocytes and local CD68+ macrophages in synovial tissues from RA patients. Upon stimulation with TNF-α, LAIR-1 expression decreased in T-helper (Th)1 and Th2 CD4+ T cells from healthy donors. These results indicate that LAIR-1 may exert different functions on T cells and monocytes/macrophages and suggest that LAIR-1 may be a novel therapeutic target for the treatment of RA.