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

Abstract

Objective: To investigate whether quantitative alterations of both beta(2)microglobulin (beta(2)micro) associated HLA class I heavy chains (sHLA-I) and beta(2) micro 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) microg/ml (mean (SD)) versus 0.8 (0.3) (p<0. 001) and 13.9 (7.1) ng/ml versus 9.2 (5) (p<0.001). sHLA-I were 1.01 (0.4) microg/ml in group A, 1.04 (0.4) microg/ml in group B, and 1. 47 (0.4) microg/ml in group C (p=0.001). Statistical analysis showed a significant difference versus controls for groups B (p<0.02) and C (p<0.001). sHLA-FHC were 12.8 (8.3) ng/ml in group A, 17.2 (7.1) ng/ml in group B, and 12.9 (6.2) ng/ml in group C (p<0.02). A significant difference versus controls for each group was found (p<0. 02, p<0.001, and p<0.02, respectively). Different patterns of sHLA-I isoforms were observed.

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.

Figure 1

Concentrations of sHLA-I and sHLA-FHC in serum of HCV infected patients and in controls. sHLA-FHC values are expressed in terms of ng/ml of bound ¹²⁵I-mAb HC-10. Each dot indicates the value of sHLA-I (panel A) and of sHLA-FHC (panel B) in a serum sample. The bars indicate means (SD).

Figure 2

Concentrations of sHLA-I and sHLA-FHC in the serum of HCV infected patients, divided by disease pattern, and in controls. sHLA-FHC values are expressed in terms of ng/ml of bound ¹²⁵I-mAb HC-10. Each dot indicates the value of sHLA-I (panel A) and of sHLA-FHC (panel B) in a serum sample. The bars indicate means (SD).

Figure 3

Relation between serum sHLA-I concentrations and cryocrit.

Figure 4

Western blot analysis of sHLA-I and sHLA-FHC isolated from sera of HCV infected patients and controls. HLA-I were immunoprecipitated by anti β₂-µ mAb NAMB-1 (panel A) from sera of HCV infected patients and controls. Lanes 1 to 3: patients with MC and CS; lanes 4-5: patients with MC without CS; lanes 6-7: patients without MC; lane 8: controls; lane 9: PBS. HLA-FHC were immunoprecipitated by anti-HLA-FHC mAB HC-10 (panel B) from sera of HCV infected patients and controls. Lanes 1-2: patients with MC and CS; lane 3: patient with MC without CS; lane 4: patient without MC; lane 5: controls; lane 6: PBS. After separation by SDS-PAGE, antigens were transferred to a nitrocellulose membrane and detected by ¹²⁵I-mAb TP25.99. PBS was used as a negative control.