Increased serum concentrations of soluble HLA-class I antigens in hepatitis C virus related mixed cryoglobulinaemia

OBJECTIVE To investigate whether quantitative alterations of both β 2 microglobulin (β 2 μ) associated HLA class I heavy chains (sHLA-I) and β 2 μ free class I heavy chains (sHLA-FHC) in sera of patients with hepatitis C virus (HCV) infection occur and whether they distinguish patients with mixed cryoglobulinaemia (MC). METHODS 83 HCV infected patients were studied and divided into three groups: (A) without cryoglobulinaemia (n=21), (B) with polyclonal MC (n=20), (C) with monoclonal MC (n=42). Serum sHLA-I and sHLA-FHC were measured by double determinant radioimmunoassay using monoclonal antibodies: TP25.99 as catching antibody, and NAMB-1 and HC-10 as revealing antibodies. Western blot identified HLA-I isoforms. RESULTS The serum concentrations of sHLA-I and of sHLA-FHC in HCV infected patients versus controls were respectively 1.3(0.5) μg/ml (mean (SD)) versus 0.8 (0.3) (p CONCLUSIONS Increased serum concentrations of sHLA-I and sHLA-FHC characterise HCV infected patients. The highest sHLA-I concentrations seem to distinguish patients with monoclonal MC. In this last condition sHLA could play a part in the HCV escape and in B cell proliferation. The significance of sHLA-FHC is still undefined.