Increased level of soluble HLA class I antigens in systemic lupus erythematosus: Correlation with anti-DNA antibodies and leukopenia

The concentration of soluble HLA class I (sHLA-I) was measured by ELISA in serum samples from 30 well-characterised SLE patients at high and low disea se activity states and from 100 healthy controls. HLA-A allotypes in the pa tients were analysed by a PCR-based typing technique. A higher level of sHL A-I was found in SLE patient sera both at high and low disease activity tha n in controls (P<0.001). The sHLA-I level was further increased during acti ve disease (P<0.01). Concentrations of sHLA-I correlated with anti-dsDNA an tibodies at high disease activity, but not with disease activity as analyse d by a modified SLEDAI. Numbers of leukocytes and lymphocytes, as well as l evels of C1q and C3 correlated inversely with sHLA-I concentration Ln five serial samples from ten patients the sHLA-I level co-varied with disease ac tivity. Presence of HLA allotype A9 was associated with higher sHLA-I level s in both patients (P<0.001) and controls (P<0.001). We conclude that the i ncreased sHLA-I concentration in SLE patients was related to several labora tory parameters reflecting disease activity suggesting that sHLA-I molecule s are connected with the disease process. Increased sHLA-I level due to HLA -A allotype was not a disease susceptibility factor for SLE. (C) 2001 Acade mic Press.