Monoclonal antibody 53.6 recognizes a novel proliferation-associated antigen encoded on human chromosome 11.

This paper describes the characterization of a novel cell surface antigen associated with proliferation. Previous work demonstrated that monoclonal antibody 53.6 reacted with every human cell line tested, as well as with subpopulations of normal bone marrow and peripheral blood lymphocytes. Mitogen stimulation of peripheral blood lymphocytes with phytohemagglutinin resulted in increased expression of the antigen recognized by 53.6. Immunoprecipitation of biosynthetically labeled KG-1A cell extracts with 53.6 revealed that the antigen is a nonglycosylated acidic protein of Mr 34,000. Analysis of mouse-human hybrid cell lines indicated that the structural gene for the antigen is encoded on chromosome 11. The antigen recognized by 53.6 is distinct from previously described cell surface antigens based on its distribution on activated cells and biochemical characteristics. These studies indicate that the 53.6 antigen is a novel proliferation-associated antigen, and may be useful in analyzing lymphocyte activation.