Changes of NK cell subsets with time post-transplant in peripheral blood of renal transplant recipients

There is evidence that NK cells with low cytotoxicity but strong immunoregulatory characteristics contribute to good graft outcome. We attempted to investigate which NK cell subsets increase post-transplant and might affect graft function.

Lymphocyte and NK cell subsets were determined in whole blood using eight-colour-fluorescence flow cytometry in patients pre-transplant and post-transplant. In total, 31 transplant recipients were studied.

When cell numbers were compared in 9 patients pre- and 6 months post-transplant, post-transplant CD56dimCD16+ (p = 0.011) NK cells with the phenotype CD158a+ (p = 0.008), CD158e+ (p = 0.038), NKG2A+ (p = 0.008), NKG2D+ (p = 0.011), IFNyR+ (p = 0.008), perforin+ (p = 0.008), granzymeB+ (p = 0.008), perforin+granzymeB+ (p = 0.008) and perforin-granzymeB- (p = 0.021) were lower than those pre-transplant, indicating a post-transplant reduction of cytotoxic NK cells. In 28 patients NK cell subsets were analyzed with respect to time post-transplant (median 888 days post-transplant). CD56dimCD16+ NK cells co-expressing CD158a (p = 0.014), NKG2D (p = 0.047), IL4R (p = 0.038), IL10R (p = 0.008) and IFNy (p = 0.036) as well as CD56bright NK cells with the phenotype TGFß+ (p = 0.017), TGFR+ (p = 0.035), CD158a+ (p = 0.042) and perforin-granzymeB- (p = 0.048) increased with time post-transplant.

Post-transplant, cytotoxic NK cells were lower than pre-transplant and remained low, whereas NK cell subsets with potentially immunoregulatory properties increased.