HIV infection leads to decreases in the number of CD4+ T lymphocytes and an increased risk for opportunistic infections and neoplasms. The administration of intermittent cycles of IL-2 to HIV-infected patients can lead to profound increases (often greater than 100%) in CD4 cell number and percentage. Using in vivo labeling with 2H-glucose and BrdU, we have been able to demonstrate that, although therapy with IL-2 leads to high levels of proliferation of CD4 as well as CD8 lymphocytes, it is a remarkable preferential increase in survival of CD4 cells (with half-lives that can exceed 3 years) that is critical to the sustained expansion of these cells. This increased survival was time-dependent: the median half-life, as determined by semiempirical modeling, of labeled CD4 cells in 6 patients increased from 1.7 weeks following an early IL-2 cycle to 28.7 weeks following a later cycle, while CD8 cells showed no change in the median half-life. Examination of lymphocyte subsets demonstrated that phenotypically naive (CD27+CD45RO–) as well as central memory (CD27+CD45RO+) CD4 cells were preferentially expanded, suggesting that IL-2 can help maintain cells important for host defense against new antigens as well as for long-term memory to opportunistic pathogens.
Joseph A. Kovacs, Richard A. Lempicki, Igor A. Sidorov, Joseph W. Adelsberger, Irini Sereti, William Sachau, Grace Kelly, Julia A. Metcalf, Richard T. Davey Jr., Judith Falloon, Michael A. Polis, Jorge Tavel, Randy Stevens, Laurie Lambert, Douglas A. Hosack, Marjorie Bosche, Haleem J. Issaq, Stephen D. Fox, Susan Leitman, Michael W. Baseler, Henry Masur, Michele Di Mascio, Dimiter S. Dimitrov, H. Clifford Lane