Expression of Leukocyte Common Antigen (CD45) on Various Human Leukemia/Lymphoma Cell Lines

CD45 antigen (leukocyte common antigen), a unique and ubiquitous membrane glycoprotein with a molecular mass of about 200 kDa, is expressed on almost all hematopoietic cells except for mature erythrocytes. However, the biological function of this glycoprotein still remains to be resolved. In order to clarify the role of CD45 antigen in hematopoietic cell differentiation and function, its expression on human leukemia/lymphoma cell lines was studied by membrane immunofluorescence. Thirty-eight established cell lines were analyzed using T29/33, a monoclonal antibody (MoAb) that recognizes the common epitopes of this glycoprotein molecule. Conventional cell marker studies were also carried out on these cell lines to compare their CD45 expression. It was shown that CD45 expression varies among B-lineage cells depending on cell differentiation, in contrast to its stable expression on leukemic T cell (6/6, positive) and myeloid (5/5, positive) lineage cell lines. On the other hand, only two out of six histiomonocytoid lineage cell lines were positive. Human T cell leukemia/lymphoma virus type I (HTLV-I)-associated T cell lines derived from peripheral blood leukocytes of patients with adult T cell leukemia/lymphoma (ALT/L) in Japan did not express CD45 on their cell surface. Taken together, these observations suggest that CD45 has a functional role in hematopoietic cell activation and differentiation.