BCL2 is a protein associated with apoptosis regulation and is produced by the bcl-2 gene located on chromosome 14q32. BCL2 consists of an alpha chain (239 amino acids) and a beta chain. BCL2 (and thus also the BCL2 alpha chain) is found in the mitochondrial and nuclear membranes and in the cytosol, but not on the cell surface. In normal lymphoid tissue, the BCL2 antibody reacts with small B lymphocytes in the mantle zone and many cells within the T cell areas. Anti-BCL2 has shown a consistent negative reaction to reactive B cells in the germinal center and positive staining of neoplastic follicles in follicular lymphoma. This antibody is valuable in distinguishing between reactive and neoplastic follicular proliferation in lymph node biopsies. This antibody can also be used to distinguish between follicular lymphomas expressing the BCL2 protein and the small number of lymphomas in which the neoplastic cells are BCL2-negative. Anti-BCL2 has been used as an indicator of minimal residual disease in the bone marrow of patients with follicular lymphoma when staining is strong and uniform. In addition, primary breast cancer is usually positive for bcl-2, which correlates negatively with P53 expression, and bcl-2-positive patients have a better prognosis.