Clinical significance of serum soluble HLA class I antigens in systemic lupus erythematosus.

Serum soluble HLA (SHLA) class I antigens in patients with systemic lupus erythematosus (SLE) were examined by enzyme-linked immunosorbent assay. The primary antibody used was W6/32, anti-HLA class I mouse monoclonal antibody, and the secondary antibody was peroxidase-conjugated anti-mouse IgG antibody. The reactivity of SHLA class I antigens, the number of peripheral lymphocytes, and the clinical state of SLE were compared. The results were as follows; 1) Sixteen of 55 samples from SLE patients were SHLA class I antigen-positive (29%). 2) The reactivity of SHLA class I antigens was closely related to disease activity. 3) The number of lymphocytes and the reactivity of SHLA class I antigens were negatively correlated. 4) Nine of 23 samples from the active SLE patients were SHLA class I antigen-negative. Of these, 7 were from patients with a nephrotic syndrome due to lupus nephritis. It is concluded that SHLA class I antigens can be an useful marker for monitoring the clinical state of SLE.