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 indu cible by interferon-alpha (IFN-alpha) on Daudi cells. To investigate t he role of p106 further, its distribution and inducibility within hema topoietic cells was studied. Multiparameter flow cytometry (FCM) analy sis showed that p106 expression was restricted to B cells and monocyte s, and in both cell lineages acquired at a late stage of differentiati on. Thus, p106 was found on mature B lymphocytes and monocytes in peri pheral 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. I n 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 t o de selective for IFN-alpha, since no other cytokines tested induced p106. Moreover, IFN-alpha therapy of chronic myeloid leukemia (CML) an d hairy cell leukemia (HCL) patients lead to a clearcut induction of p 106 on such malignant cells. The distribution of p106 could suggest th at it represents an activation antigen. Further studies, including clo ning of p106 cDNA, are needed to determine the function of p106.