Expression and regulation of an interferon-alpha-inducible membrane protein p106 on human hematopoietic cells

p106 is a human membrane protein of 106 kD previously shown to be inducible by interferon-alpha (IFN-alpha) on Daudi cells. To investigate the role of p106 further, its distribution and inducibility within hematopoietic cells was studied. Multiparameter flow cytometry (FCM) analysis showed that p106 expression was restricted to B cells and monocytes, and in both cell lineages acquired at a late stage of differentiation. Thus, p106 was found on mature B lymphocytes and monocytes in peripheral blood and on a variety of freshly isolated leukemic cells of B and myeloid origin as well as on a variety of cultured B-cell lines. In contrast, no expression was found on T lymphocytes, natural killer (NK) cells or granulocytes. p106 expression could be further induced by IFN-alpha on monocytes and Daudi cells, and this capacity was shown to be selective for IFN-alpha, since no other cytokines tested induced p106. Moreover, IFN-alpha therapy of chronic myeloid leukemia (CML) and hairy cell leukemia (HCL) patients lead to a clearcut induction of p106 on such malignant cells. The distribution of p106 could suggest that it represents an activation antigen. Further studies, including cloning of p106 cDNA, are needed to determine the function of p106.