Aim: To investigate the expression of NKG2D ligands on dendritic cells(DC) at different development stages and its effect on cytotoxicity of natural killer(NK) cells.
Methods: The monocytes were cultured into immature dendritic cells(iDC) and mature dendritic cells(mDC) with cytokines. NK cells were obtained from normal peripheral blood by CD56 antibody magnetic isolation.The expression of NKG2D ligands (MICA/B, ULBP1-3) was detected by flow cytometry. Cytotoxicity of NK cells and the NK cells blocked with anti-NKG2D mAbs against iDC and mDC was tested using LDH-releasing method.
Results: IDC and mDC were of typical morphology and phenotypes. MICA, MICB, ULBP1, and ULBP3 were expressed on iDC and their expression rate was (32.39+/-8.30)%, (17.75+/-3.40)%, (26.71+/-6.48)%, (38.37+/-6.89)%, respectively. MICA and ULBP3 were expressed on mDC and their expression rate was (7.81+/-3.33)% and (8.36+/-2.42)%, respectively, which was lower than that on mDC (P<0.01). At the each E:T ratio cytotoxicity of NK cells against iDC was stronger than that against mDC (P<0.01). cytotoxicity of NK cells blocked with anti-NKG2D mAb against iDC was decreased compared with that of NK cells unblocked (P<0.05) while cytotoxicity of NK cells blocked with anti-NKG2D mAb against mDC showed no decrease compared with that of NK cells unblocked (P>0.05).
Conclusion: The expression of NKG2D ligands on iDC is higher than that on mDC, which plays an important role in the cytotoxic effect of NK cells against iDC, but has no effect on that against mDC. NKG2D-NKG2D ligands shows one of the molecular mechanisms that NK cells kill iDC selectively.