Fig. 7. Antibody-dependent and -independent xenorecognition of NK cells. (A) NK cells can facilitate the destruction of porcine cells through antibody-dependent cytotoxicity and (B) antibody-independent direct cytotoxicity. In the antibody-dependent cellular cytotoxicity process, NK cells interact with the Fc region of antibody complexes via FcRs, leading to the release of cytotoxic granules. In the antibody-independent, direct cytotoxicity, the inhibitory receptors on human NK cells, including KIR, ILT2, and CD94/NKG2A, fail to effectively recognize SLA-I and the pig HLA-E counterpart, which blocks the inhibitory signals that would typically suppress NK cell activity. Additionally, the engagement of pULBP1-NKG2D and pCD58-CD2 signaling pathways, along with an unknown ligand interacting with NKp44, can induce the direct cytotoxic activity of NK cells. NK, natural killer; FcR, Fc receptor; α-Gal, α-galactosidase; KIR, killer cell immunoglobulin-like receptor; SLA, swine leukocyte antigen; HLA, human leukocyte antigen.
Clin Transplant Res 2024;38:273~293 https://doi.org/10.4285/ctr.24.0056