Elevated level of soluble HLA class I antigens in serum and bronchoalveolar lavage fluid in patients with sarcoidosis.

Objective: Soluble HLA class I antigens (sHLAs) in human serum have been reported to be associated with allografts and autoimmune disease and could modify immunological reactions induced by membrane type HLAs. To investigate the clinical significance of sHLAs in sarcoidosis, we assessed concentrations of sHLAs in both serum and bronchoalveolar lavage fluid (BALF) and also examined their production by peripheral blood mononuclear cells (PBMCs) and BALF cells.

Methods: Concentrations of sHLAs were determined by enzyme-linked immunosorbent assay, using a monoclonal antibody against HLA class I (W6/32) and an enzyme-labeled polyclonal antibody to human beta2-microglobulin. PBMCs and BALF cells were cultured in the presence or absence of either LPS or PHA.

Patients: Serum levels of sHLAs were assessed in 96 patients with sarcoidosis and in 32 healthy control subjects. sHLAs concentrations in BALF were also investigated in 17 active sarcoidosis patients and in 13 control subjects.

Results: sHLAs levels in both serum and BALF were higher in sarcoidosis cases than in control subjects (p<0.05, in both). In the patients, values were significantly higher in active than in inactive stages (p<0.001) and significantly correlated with angiotensin-converting enzyme (ACE) levels. Both PBMCs and BALF cells produced enhanced amounts of sHLAs in patients with active sarcoidosis compared with those in control subjects.

Conclusion: These results demonstrated that the level of sHLAs in serum is a useful index of disease activity of sarcoidosis, partly reflecting production by PBMCs and BALF cells.