Different production of soluble HLA-G antigens by peripheral blood mononuclear cells in ulcerative colitis and Crohn's disease: A noninvasive diagnostic tool?

Background: HLA-G antigens are nonclassical major histocompatibility complex (MHC) class I molecules characterized by tolerogenic and antiinflammatory properties. Recently, a different expression of HLA-G antigens has been observed between intestinal biopsies of ulcerative colitis (UC) and Crohn's disease (CD) patients. These data suggested a functional role for HLA-G molecules in the diseases and proposed the HLA-G modulation as a marker for the diagnosis of UC and CD. The soluble HLA-G antigens (sHLA-G) are circulating molecules mainly produced by activated peripheral blood CD14+ monocytes. Methods: We tested, by specific enzyme-linked immunosorbent assay (ELISA), the sHLA-G molecule levels in the supernatants of unstimulated and bacterial lipopolysaccharide (LPS)-stimulated cultures of peripheral blood mononuclear cells (PBMC) from 30 healthy subjects, 10 CD, and 18 UC patients. The data were not influenced by treatment or disease activity. Results: The results confirmed a different sHLA-G expression between the diseases, with a spontaneous secretion of sHLA-G in CD patients but not in UC and healthy subjects. Moreover, a lack of sHLA-G antigens has been reported in UC patient cultures after LPS activation but not in healthy subjects and CD patients. The defective sHLA-G production was related to an impaired IL-10 secretion in UC but not in CD. Conclusions: Overall, these results confirm the presence of a different biological characteristic between CD and UC patients and suggest sHLA-G production by PBMC as a noninvasive diagnostic tool in the early phases of the diseases.