Natural Killer (NK) cells are of special interest in solid organ
transplantation (SOT) because classical immunosuppressive drugs
could enhance NK cells activity.We studied NK cells after kidney
transplantation in three different situations. First, we analysed the
peripheral repertoire reconstitution and function of NK cells after
a polyclonal rabbit anti-thymocytes globulin (rATG) induction
therapy, in 20 patients transplanted with living donor and with
a low immunological risk. Second, we analysed the influence
of KIR genes on the risk of CMV primo-infection or reactivation
in 224 transplanted patients during the first year. Finally,
we studied the risk of rejection and graft function during the
first 5 years according to the KIR genes. Our study demonstrates
that after an intial drop, NK cell reconstitution is fast with a
ratio of CD56+/CD3− cells versus CD3+ cells that remains
identical. The fraction of NK cells expressing the inhibitory
receptor NKG2A significantly increases and the activating receptor
NKG2D decreases after transplantation to retrieve the pretransplantation
value after one year. The secretion of INF-f ×
and the cytotoxicity is maintained over time after transplantation.
Then, we demonstrated that the presence of 2 KIR missing ligands
and a large number of activating KIR gene protected against
CMV primo-infection or reactivation during the first year post
transplantation. Finally, the KIR genes and their HLA ligands do
not influence the long term graft function after univariate and multivariate
analysis. Our data suggest that despite the modification
of the receptor repertoire, NK cell activity is preserved. NK cells
are an important player of the immune response in the first year
after transplantation mainly thanks to their anti-infectious activity.