Add Publication. S100A12, a newly discovered member of the S100 family of calcium regulatory proteins, is located within the same gene cluster on chromosome 1q21 as other S100A family members. In humans, S100A12 is mainly secreted by neutrophils and monocytes, but can also be expressed by tissue cells, such as mucosal epithelial cells and keratinocytes. Rodents do not express S100A12.