PCNA/HLA I complex interaction with NKp44 inhibits NK92-MI Cell Cytotoxic Function.

<p>The lysis of DB cells by NK92-MI cells was determined by a standard ⁵¹Cr release assay. DB cells and NK92-MI cells were first blocked with Human IgG Fc fragment to prevent reverse binding of fusion protein and antibody dependent cellular cytotoxicity. DB cells were loaded with ⁵¹Cr and incubated with 1 µg/ul of NKp44-Ig (<b>4A</b>) or 0.5mg/ml anti-PCNA (<b>4B</b>) or anti-HLA I (<b>4C</b>). DB cells were then incubated with NK92-MI cells at varying target to effector cell ratios for 4 hours at 37°C. Level of killing was compared to DB cells incubated with 0.5 mg/ml mIgG2a isotype antibody or no antibody, which served as a positive control (No Blocking) of cell lysis under unblocked conditions. Alternatively, NK92-MI cells were incubated with 0.5 mg/ml anti-NKp44 or mIgG1 isotype control antibody prior to incubation with DB cells incubated with no antibody (<b>4D</b>) or 0.5 mg/ml anti-HLA I (<b>4E</b>). Figure is representative of two independent experiments performed in triplicate. Bars ± SD. *p<.05, **p<.01, ***p<.0001, ANOVA.