S100A8 is a member of the S100 family of proteins. S100 proteins are localized in the cytoplasm and/or nucleus of a wide range of cells, and involved in the regulation of a number of cellular processes such as cell cycle progression and differentiation. S100A8 may function in the inhibition of casein kinase and as a cytokine. Outside of malignancy, S100A8 in association with its dimerization partner S100A9 signals for lymphocyte recruitment in sites of inflammation. S100A8/A9 are also regarded as marker proteins for a number of inflammatory diseases in humans, especially in rheumatoid arthritis and inflammatory bowel disease.