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HORDES of killer cells intent on destroying cancerous or infected cells could
one day be injected into patients, thanks to a breakthrough that makes it far
easier to grow them outside the body.

Our bodies naturally produce killer cells, also known as cytotoxic T
lymphocytes or CTLs, which target tumours or virus-infected cells. But the
immune response is sometimes too weak or patients are too ill to produce enough
CTLs. So in experimental treatments called adoptive immunotherapy, specific
immune cells from a patient are purified, encouraged to multiply and then
reinjected. However, doctors are struggling to make such treatments practical.
The cells require months of growth with special protein factors or a complex mix
of companion 鈥渇eeder鈥� cells.

Now Carl June of the Abramson Family Cancer Research Institute in
Philadelphia and his colleagues have designed a better cell to nurture CTLs, by
decking an antigen-presenting cell鈥檚 surface with a smorgasbord of proteins
thought to encourage CTL growth.

The new improved CTL companions, which June calls artificial
antigen-presenting cells or aAPCs, generated 400 times more CTLs than the most
popular purified protein factor, and unpublished data suggests they are just as
efficient as feeder cells鈥攖he gold standard in this field. What鈥檚 more,
from a patient immunised with flu vaccine, June鈥檚 team was able to grow a full
dose of CTLs in just 30 days that should kill flu-infected cells.

Mark Dudley, an adoptive immunotherapy researcher at the National Cancer
Institute in the US, says aAPCs are a major advance. 鈥淏ecause they are so easily
altered, these cells will allow a systematic way to find out how to generate the
best CTL responses,鈥� he says. June hopes to be ready for a trial in a few years.
And he thinks his team could eventually use aAPCs to produce enough CTLs in just
two weeks. 鈥淪ometimes this therapy is used to treat really sick patients,鈥� he
says. 鈥淎nd they can鈥檛 wait any longer.鈥�