Figure 2. CD107a degranulating assay on distinct NK cell subsets expressing single inhibitory receptors.

CD107a degranulating ability of activated NK cell subsets from each patient was analyzed in the presence of autologous melanoma cells, either adding or not an anti-pan HLA class I blocking mAb. E/T ratio = 1.5∶1. A representative analysis of patient CA is shown in panel A. In order to assess the link between HLA class I expression on melanoma cells and their susceptibility to autologous NK cell-mediated lysis, the degranulation of NK cell subsets, expressing a single inhibitory receptor for distinct HLA class I molecules, was analyzed. Staining NK cells with mAbs against a specific KIR or NKG2A and with a mixture of mAbs against the other inhibitory receptors allowed to gate on the specific subset and evaluate its CD107a expression after co-culture with autologous melanoma cells. B: Melanoma specific deletion of a HLA class I allele in the same patient CA. HLA-Bw4 was here detected by flow cytometry on the surface of lymphocytes but not of the autologous melanoma. As a comparison, another conserved HLA-A allele is shown. In accordance with Bw4 deletion, KIR3DL1+ NK cell subset exerts a strong cytolytic activity against autologous melanoma cells, which is not significantly increased following anti-HLA class I masking.