Expression of Dipeptidylpeptidase IV (DPP IV/CD26) Activity on Human Myeloid and B Lineage Cells, and Cell Growth Suppression by the Inhibition of DPP IV Activity

Abstract

Human CD26 antigen is a transmembrane glycoprotein with dipeptidyl peptidase IV (DPP IV) activity in its extracellular domain. Within the hematopoietic system, CD26/DPP IV has been thought to be exclusively expressed in activated T and NK cells [1]. However, by enzymatic assay, Bauvois et al. have characterized DPP IV activity (sensitive to diprotin A which is the specific inhibitor of DPP IV) present on the surface of human myeloblastic HL-60 and monoblastic U937 cell lines as well as on peripheral monocytes, granulocytes and macrophages [2]. Moreover, DPP IV activity increased strictly on cells undergoing macrophage maturation [2]. Reinhold et al. found that synthetic reversible inhibitors of DPP IV suppressed cell proliferation and modulated cytokine production in U937 cells expressing high levels of CD26 [3]. Monoclonal antibody (mAb) anti-Tal (purchased from Coulter, Hialeah, FL) and directed against CD26 of activated human T cells was recently shown to react with a few B cell lines including Daudi cells which are tumor cells derived from Burkitt lymphoma and EBV-transformed cells [4]. Another anti-CD26 mAb i.e. anti-TA5.9 (from Eurogenetics, Tessenderlo, Belgium) was shown to bind activated T cells as well as myeloid cells, Raji and U266 cells [5].