Introduction Though of dual function, CD72 is appreciated for being a regulatory receptor on B cells. B cell receptor (BCR) -mediated signals are enhanced when CD72 expression is deficient on B cells in both animal models and autoimmune diseases such as systemic lupus erythematosus (SLE). The significance of soluble CD72 (sCD72) has not been elucidated.
Methods We evaluated and compared the presence of sCD72 in the serum of patients with SLE and healthy individuals in order to ascertain whether sCD72 serum level is increased in SLE patients, using specific ELISA. Possible correlation was assessed between increased sCD72, SLE disease activity (SLEDAI), renal involvement and SLE related autoantibodies.
Results The serum level of sCD72 in 159 SLE patients was found to be significantly increased compared to that of 80 healthy individuals (20 ± 1.2 ng/ml vs 8.2 ± 0.4 ng/ml; p < 0.001). Soluble CD72 levels were significantly higher in patients positive for double –stranded DNA (dsDNA) antibodies than that in patients without (23±1.5ng\ml vs 14.1±1.4ng\ml; p=0.003), also for anti-cardiolipin Ab (aCL) (28.5±3.1ng\ml vs 15.2±1.8ng\ml; p < 0.005); the levels were also significantly higher in patients with lupus nephritis than that in patients without (31.8 ± 2.3 ng/ml vs 13.9 ± 0.9 ng/ml; p < 0.001). Finally, sCD72 correlated positively with SLE disease activity (r = 0.703; p < 0.001).
Conclusion Soluble CD72 is significantly increased in SLE patients. It is a possible marker for renal involvement, aCL and anti-dsDNA antibodies positivity in SLE and in positive correlation with SLE disease activity.