THE VALUE OF IMMUNOHISTOCHEMISTRY
IN THE ASSESSMENT OF BONE MARROW DISORDERS

Attilio Orazi, M.D., FRCPath. and Dennis P. O'Malley, M.D.

DBA.44 DBA.44 is a mouse monoclonal antibody made against a large B-cell lymphoma cell line. It has been considered to be specific for hairy cell leukemia (HCL) but also reacts with cells of the mantle zone and some germinal center cells. It also cross reacts with alveolar lining cells, kidney tubular cells, and some salivary duct cells. Although DBA.44 is positive in the vast majority of hairy cell leukemias, it is not specific and stains many cases of large B cell lymphomas and occasional T cell lymphomas. However, marginal zone lymphoma cells (including splenic marginal zone lymphoma) are usually negative. The stain appears to work well in both formalin and B5 fixed tissue and is resistant to decalcification. The antigen staining is improved by using a heat-induced epitope retrieval technique or with proteolysis. DBA.44 can be used to support a morphologic diagnosis of hairy cell leukemia. Since normal bone marrows contain a small but variable number of DBA.44 positive cells, the marker is of limited use in determining minimal residual disease in post-treatment biopsy specimens of patients with hairy cell leukemia . References Hounieu et al. Hairy cell leukemia. Diagnosis of bone marrow involvement in paraffin-embedded sections with monoclonal antibody DBA.44. Am J Clin Pathol. 1992; 98:26-33. Ellison et al: Immunomorphologic analysis of bone marrow biopsies after treatment with 2-chlorodeoxyadenosine for hairy cell leukemia. Blood. 1994 Dec 15;84(12):4310-5.