To investigate the relationship between surface and soluble SIGLEC-1 levels, we immunophenotyped the expression of this protein on the surface of CD14+ monocytes in PBMCs collected from a discovery cohort (cohort 1) of 34 SLE patients and 24 matched healthy donors (Fig. 2a). This evidence concerns the gene SIGLEC1 and systemic lupus erythematosus.