Here we have investigated the portion and activation status of several leukocyte subpopulations and measured cell surface S100A8/A9 on these cells, corresponding S100A8 and S100A9 mRNA expression as well as serum levels of S100A8/A9 in healthy controls and SLE patients to learn more about the role of these proteins in SLE. This evidence concerns the gene S100A9 and systemic lupus erythematosus.