Submitted March 27, 2007
Accepted July 11, 2007
Notch signaling induces cytoplasmatic CD3
expression in human differentiating NK cells
Magda De Smedt, Tom Taghon, Inge Van de Walle, Greet De Smet, Georges Leclercq, and Jean Plum*
Department of Clinical Chemistry, Microbiology & Immunology, Ghent University, Ghent, Belgium
* Corresponding author; email: jean.plum{at}ugent.be.
It has been proposed that heterogeneity in NK cell phenotype and function can be achieved through distinct thymic and bone marrow pathways of NK cell development. Here we show a link between Notch signalling and the generation of intracellular CD3
(cyCD3) expressing NK cells a population that can be detected in vivo. Differentiation of human CD34+ cord blood progenitors in IL-15 supplemented foetal thymus organ culture or OP9-DL1 coculture resulted in a high percentage of cyCD3+ NK cells that was blocked by the 
-secretase inhibitor DAPT. The requirement for Notch signalling to generate cyCD3+ NK cells was further illustrated by transduction of CD34+ CB cells with either the active intracellular part of Notch or the dominant negative mutant of Mastermind like protein 1 that resulted in the generation of NK cells with respectively high or low frequencies of cyCD3. Human thymic CD34+ progenitor cells displayed the potential to generate cyCD3+ NK cells even in the absence of Notch/DL1 signalling. Peripheral blood NK cells were unable to induce cyCD3 expression after DL1 exposure, indicating that Notch-dependent cyCD3 expression can only be achieved during the early phase of NK cell differentiation.
