Increased serum concentration of soluble HLA-DR antigens in HIV infection and following transplantation

Abstract: HLA class I and class II antigens circulate in serum as soluble molecules. Increased concentrations of soluble HLA class I molecules have been demonstrated in viral diseases, in rejection episodes following organ transplantation and in graft versus host disease. To explore the possibility of a variation of the serum concentrations of soluble HLA class II molecules in the same pathologic conditions we developed a double determinant immune assay that detects whole soluble HLA-DR molecules (sHLA-DR). The mean level of sHLA-DR antigens in sera from 23 healthy individuals was 0.64±0.72 μg/ml. Elevated serum concentrations of sHLA-DR molecules were detected in sera from HIV infected patients in CDC2/3 and in CDC4C1 stages (2.0±1.7 g/ml and 4.6±1.7 g/ml, respectively), in sera from patients affected by acute rejection after liver transplantation (5.3±3.7 μg/ml) and in sera from patients affected by severe acute graft versus host disease following bone marrow transplantation (8.8±3.1 μg/ml). The increase of sHLA-DR molecules in these sera significantly correlated with the elevation of soluble HLA class I antigens (P=0.0004). The reported data suggest that both soluble HLA class I and class II molecules serum levels increase during viral infections and strong immune reactions and could suggest the involvement of these molecules in immunoregulation.