That argument did not sit well with Louis J. Picker, associate director of the Vaccine and Gene Therapy Institute at Oregon Health Sciences University in Portland. "The proliferation studies [used to measure the presence of CD4+ T cells] have a six-day readout time," he says. "It's been shown that you're measuring the overall ability of T cells to proliferate under those conditions." In other words, cells that don't thrive in vitro might die in culture. At the experiment's end, those cells would be under-represented, leading researchers to conclude mistakenly that little or no CD4+ T cells were present in the sample.2
Picker and his colleagues got to work trying to "assess the hypothesis that HIV-specific memory CD4+ T cells were absent in active HIV infection, either because they developed but were killed off or perhaps because they never developed," he says. "The absence of these cells was being touted as ...
