Zeta’s mouse monoclonal antibody recognizes Annexin A1. The Annexin A1 (ANXA1) gene belongs to the annexin family, and contains 4 annexin repeats, where the pair of annexin repeats may form one binding site for calcium and a phospholipid. Annexin A1 (ANXA1) promotes membrane fusion and is involved in exocytosis. The gene for Annexin A1 (ANXA1) is upregulated in hairy cell leukemia (HCL), and its protein expression is specific for HCL. Detection of Annexin A1 (ANXA1) provides a simple, highly sensitive and specific assay for diagnosing HCL. Annexin A1 has also been found to be protective against DNA damage induced by heat in breast cancer cells, suggesting Annexin A1 is involved in tumor suppressive and protective activities, and also is associated with treatment resistance.