Natural Killer Cell Tolerance Persists Despite Significant Reduction of Self MHC Class I on Normal Target Cells in Mice
Kb single mice were injected with CFSEhigh B6.Tap−/− cells unpulsed or pulsed with Mulv peptide, mixed with CFSElow syngeneic control cells. The cells were stained for Kb at the time of inoculation, and the Kb MFI level in % of the syngeneic controls was calculated. These values are indicated on the x axis. The rejection was assessed in the spleen after 8 hrs, and is shown on the Y axis. CFSE ratio between target cells and syngeneic controls was calculated relative to the NK1.1 treated group in each experiment, to compensate for inter-experimental variation. Each dot represents the mean of 2 mice/group in each experiment, with total n = 32 mice for the Tap+Mulv groups and n = 23 mice for unpulsed Tap−/− groups (NK depleted and non-depleted). The dashed line indicates the minimal amount of killing of unpulsed cells that occurred in any experiment. Data in the graph were obtained from a total of 8 experiments. The difference between rejection of unpulsed and Mulv pulsed cells was statistically significant (P = 0.0018 for all experiments with an induced Kb expression of at least 23% of control, compared to NK1.1 controls in the same experiments).