The biggest and most important symbol in this fascinating work of non-fiction are the cells that were taken from Henrietta's cervix, without her knowledge, so long ago. By some curious design, they are cells that are, as the title indicates, immortal, and this is the very crux of the novel: the character of Henrietta Lacks and her suffering is something all of us have so much to be thankful for. Even though Henrietta died long ago, her life is still worth remembering out of thanks for the advances that have been achieved in medicine through her cells. This is most poignantly referred to when the author records Deborah's last words to her about death, who was Henrietta's daughter:
I don't want to be immortal if it mean living forever, cause then everybody else just die and get old in front of you while you stay the same, and that's just sad... But maybe I'll come back as some HeLa cells like my mother, that way we can do good together out there in the world.
The HeLa cells are powerful and important symbols of immortality and the way that one formerly unknown black woman's life has managed to change the face of medical science. She, against all the odds, has gained immortality for herself in a world where she wasn't valued or treated as anybody special, least of all by the medical establishment that gained so much from her.