Normally, the body kills HIV-infected cells. But it misses these, because they look perfectly normal. The similarity makes the infected cells almost impossible to kill with any drugs. Siliciano has been counting these cells in his Baltimore volunteers for five years. Siliciano said he favors the first theory.
Immunological memory lasts forever.
This is why someone who catches measles in childhood will remain immune to the disease into old age. Memory cells may die over time, but they also make replacements by cell division. And every time a memory cell divides, it faithfully reproduces the HIV that is stitched into its genes. However, the Diamond Center's Ho prefers the second theory. Memory cells are much shorter lived, he said.