Expression of activating Killer Ig-like receptors on natural killer cells: is more really better? Grant proposal for a pre-clinical study to optimize future donor selection protocols for pediatric acute B cell precursor leukemia patients.

20.08.2016 bis 19.08.2018

Despite the remarkable progress that has been made in curing childhood acute B cell precursor leukemia (BCP-ALL), long-term remission is achieved in only 80% of the children. Therefore, alternative therapeutic strategies such as the exploitation of natural killer (NK) cell-mediated anti-tumor responses have recently come into the focus of clinical researchers. NK cell activity is importantly controlled by the Killer Ig-like receptor (KIR) family that comprises both inhibitory (iKIR) and activating (aKIR) family members. Recent data of others and our group indicate that the selection of a donor with defined iKIR expression will beneficially affect the prognosis of children when they lack the expression of the respective ligands (so-called KIR-KIRL mismatch). In contrast, the evidence for beneficial effects of aKIR expression on NK cells is currently insufficient. Association studies suggest selecting a donor who possesses aKIRs next to iKIRs and who should ideally express not one but multiple aKIRs. However, due to the lack of aKIR-specific monoclonal Abs, it has never been defined how the ideal alloreactive aKIR+ NK cell subset should phenotypically look like and what functional properties it should have. Fortunately, we have recently been enabled to use various aKIR mAbs produced by D. Pende, Genua, and have succeeded in implementing a complex multi-color flow cytometric detection of iKIRs together with aKIRs (“double fluorescence analysis”) and in applying a Boolean gating strategy (SPICE analysis) to further interpret the information. Thus, we can now visualize not only the distribution of cells responding with different numbers of distinct responses (NKGA-iKIR+single aKIR+ versus NKG2A-iKIR+multiple aKIR+) but also the nature of individual responses (which subset responds in which way: CD107a+, IFN-γ+ or both). Thus, we would here like study in vitro in co-culture experiments and in vivo in immune-permissive NOD SCID IL2Rγc-/- (NSG) mice 1. to what extent aKIRs really contribute to target cell recognition and 2. what implications aKIRs will have in the KIR-KIRL mismatched setting when patients lack at least some of the HLA class I determined aKIR ligands.