Decreased production of human leukocyte antigen G molecules in sinonasal polyposis

Sinonasal polyposis (SNP) is a chronic inflammatory pathology of nasal and paranasal cavities. Human leukocyte antigen (HLA) G molecules are nonclassic class I antigens with anti-inflammatory and tolerogenic properties. As most theories consider polyps to be the manifestation of chronic inflammation, there could be a possible implication of HLA-G molecules in SNP. The purpose of this study was to investigate the possible correlation between SNP and the production of soluble HLA-G (sHLA-G) by peripheral blood mononuclear cells (PBMCs).

The study involved 22 SNP patients (11 with no evidence of disease [NED] after surgery and 11 with relapse [RE]) and 20 healthy subjects. The presence of sHLA-G in PBMC lipopolysaccharide (LPS)-stimulated culture supernatants was analyzed. The levels of interleukin (IL) 10, one of the main up-regulators of sHLA-G production, were determined. Exogenous IL-10 was added to the SNP PBMC cultures to reconstitute the impairment in sHLA-G production.

Increased IL-10 levels in LPS-activated PBMC culture supernatants were found in NED patients in comparison with healthy subjects (p = 0.0184). No sHLA-G production was observed in either of the patient subgroup supernatants (p < 0.0001). The addition of exogenous IL-10 showed the reconstitution of sHLA-G production in NED and in a lower amount in RE patients.

The results show a defect in sHLA-G production in SNP patients mainly related to the IL-10/HLA-G pathway. Given the anti-inflammatory functions of HLA-G molecules, this impairment could increase the susceptibility to the disease. The different sHLA-G production after exogenous IL-10 addition between NED and RE SNP could represent a marker of disease severity.