NK Cells (Large Granular Lymphocytes)
- Can lyse tumor cells or virus infected
cells without prior sensitization; insert pore forming
proteins (perforins) into victim, making them leaky
- CD16: all NK cells and granulocytes;
low affinity Fc receptor
- CD56 (Leu19) and CD2 positive
- CD3 negative
- K cells, which mediate antibody-dependent
cell-mediated cytotoxicity, are probably a subset
of NK cells
Fig. 5-4
Schematic representation of NK cell receptors and killing. Normal cells are not
killed because inhibitory signals from MHC class I molecules override activating signals.
In tumor cells or virus-infected cells, reduced expression or alteration of MHC molecules
interrupts the inhibitory signals, allowing activation of NK cells and lysis of target cells.
