Natural killer (NK) cells are important
players of the innate immune system. While they are best known for their
ability to protect against virus infections and tumors, not much is known about
their role in bacterial infections.
Urinary tract infections are commonly
caused by Uropathogenic Escherichia coli. Around 50% of all women and
12% of men will experience this infection in their life-time.
Incubation of NK cells with several E.
coli strains led to an adherence of the bacteria to the cells at 4oC and to killing of
the NK cells by the bacteria at 37oC. The adherence ability was found to be a
common trait of various tested E. coli strains however the strains which
killed NK cells were associated with urinary tract infections.
Transposon mutagenesis of UPEC CFT073 revealed
that type I fimbriae mediates the attachment to NK cells and hemolysinA
expressed by UPEC was responsible for killing the NK cells.
We demonstrated, both in vitro and
in vivo, that in the absence of hemolysinA NK cells respond directly to
the presence of the bacteria by secreting TNFα leading to a reduction in the
numbers of colonizing UPEC.
Thus we show that NK cells participate in
protection against urinary tract infections and that UPEC evades this immune
response by killing the NK cells.
