Figure 1.

Potential role for NK cells in promoting allograft rejection. NK cells can contribute to allograft rejection in several ways: (A) By mediating direct cytoxicity against cells of the allograft that increasingly express cellular-stress or virus-associated activating ligands. (B) Via antibody-dependent cellular cytoxicity upon binding of CD16 on the NK cell to anti-HLA antibodies. (C) By producing proinflammatory cytokines like IFN-ϒ, that promote Th1 polarization of CD4⁺ cells, priming and activation of CD8⁺ T cells directed against the allograft and by stimulating B cell production of pathogenic IgG antibodies. iNKR, inhibitory NK cell receptor; aNKR, activating NK cell receptor.