Increased level of serum HLA class I antigens in patients with systemic lupus erythematosus. Correlation with disease activity

The level of soluble beta(2)-mu-associated HLA Class I heavy chains (sHLA-I) and of soluble beta(2)-mu-free HLA Class I heavy chains (sHLA-FHC) was found to be significantly higher in sera from 58 patients with systemic lupus erythematosus (SLE) than in those from 82 age and sex-matched controls, The level of serum sHLA-I in patients with SLE was significantly correlated to disease activity. Western blotting analysis showed that the 44- kDa isoform represents the major component in the antigens immune precipitated by anti-beta(2)-mu mAb NAMB-1 and by anti-beta(2)-mu-free BLA Class I heavy chain mAb HC-10 from sera of patients with SLE. These results suggest that the increased serum levels of sHLA-I and of sHLA-FHC in patients with SLE reflect their increased shedding from cell membrane. In view of the ability of sHLA-I and of sHLA-FHC to induce apoptosis of activated T cells, it is suggested that their increased serum levels in patients with SLE is triggered by dysregulation of the immune system leading to T-cell activation. The increased serum levels of sHLA-I and of sHLA-FHC may be used by the immune system to central the pool of activated T cells by inducing apoptosis. If this possibility is proven to be correct, modulation of the serum level of sHLA-I and of sHLA-FHC may be utilized to develop strategics to treat SLE.