Abstracts (complete list) - Wissenschaft Online

Eva Schlecker, Isabel Hartmann, Michael Ackmann, Elisabeth Weiss
KIR2DS2 and interaction with DAP12
The KIR locus is characterized by fluctuating gene content, which mainly depends on
the presence or absence of activating KIRs, and allelic variation. Whereas the function
and ligands of the inhibitory KIRs have been extensively studied, similar facts are
lacking for the activating KIRs. Several studies have demonstrated that activating KIRs
might be involved in the progression of autoimmune disease and also play a role in
transplantation situations. For most of the activating receptors no ligands have been
identified yet. We tried to establish a cell based read-out system to identify ligands for
activating KIRs by coexpression of KIR2DS2 and DAP12 in Jurkat and HEK 293T cells in
the presence of luciferase reporter vectors regulated by NFAT or a minimal IFNgamma
promoter.
In HEK293T cells DAP12 was higly expressed at the cell surface even in the absence of
KIR2DS2. Thus, DAP12 cell surface transport does not need transmembrane partners or
DAP12 associates with a yet unknown polypeptide in these cells. KIR2DS2 was only
weakly detected at the cell surface in both transfectant cell types. It is possible that the
GL183 antibody does not recognize KIR2DS2 efficiently. Cross-linking of KIR2DS2,
DAP12 or KIR2DS2/DAP12 did not result in the activation of the luciferase reporter
vectors. Moreover, no tyrosine phosphorylation of DAP12 was detected, whereas using
antibody stimulation of cells expressing hybrid CD3zeta/CD94 and NKG2A molecules
resulted in tyrosine phosphorylation of CD3zeta. We conclude that on the one hand the
low binding of the GL183 antibody to KIR2DS2 might be responsible for the lack of
activation, as several studies have shown that interactions between low-avidity ligands
could induce an inhibitory signal by recruiting SHP1 to the signalling ITAM complex and
that DAP12 can also inhibit cellular activation. On the other hand, the association of
KIR2DS2 with DAP12 might also trigger a repressive state.