Recognizes a protein of 14-16kDa, which is a novel nuclear antigen of proliferating cells. IPO-38 antigen is present in the nuclei of proliferating cells such as Hodgkin's disease and non-Hodgkin's lymphomas, different forms of leukemias, breast and colorectal carcinomas, and PHA-stimulated lymphocytes. It is not expressed in the cells of non-stimulated lymphocytes and granulocytes. IPO-38 may be a useful marker of cell proliferation during monitoring of tumor progression.