Higher expression of latency-associated peptide on the surface of peripheral blood monocytes in patients with rheumatoid arthritis may be protective against articular erosions.

Latency-associated peptide (LAP) forms small latent complexes with transforming growth factor beta 1 (TGF-β1). TGF-β-LAP complexes can be detected on the surfaces of immune cells and have been recently shown to play a role in immune regulation through TGF-β1-mediated functions. A study was undertaken to investigate the correlation of LAP expression on the surface of immune cells and presence of articular erosions in patients with rheumatoid arthritis (RA). Venous blood was obtained from patients with severe RA as well as from healthy control subjects. Surface expression of LAP on peripheral blood mononuclear cells was analyzed by flow cytometry, measured as flow cytometric intensity separately on CD14(+) and CD14(-) cells, and compared between RA patients and healthy subjects. Patients with RA demonstrated higher surface expression of LAP on both CD14(+) and CD14(-) mononuclear cells than healthy individuals. Patients with erosive RA had significantly reduced intensity of anti-LAP staining on the CD14(+) cells when compared to RA patients without erosions (p = 0.01). The intensity of anti-LAP staining on CD14(-) cells was not different between groups of RA patients. Higher expression of LAP on the surface of the cells of monocyte lineage may be protective of formation of articular erosions in RA. Further studies are needed to elaborate the mechanism of this phenomenon.