SIGLEC1 and systemic lupus erythematosus: Several studies demonstrated that expression of SIGLEC-1 as a surface molecule of monocytes was a promising biomarker [9,10,36,37]; however, only Oliveira et al. investigated serum levels of soluble SIGLEC-1 in SLE and concluded that sSIGLEC-1 reflected the expression on monocytes that was not found to be correlated with disease activity [13].