We’ve been talking about Proleukin (interleukin-2, or IL-2, used to treat melanoma and kidney cancers) for more than 15 years. We had hoped that, by raising people’s CD4 cell counts, the experimental immune-based therapy could supplement antiretroviral meds for HIV. But now IL-2 has been shot down: In studies, positive people did no better with Proleukin plus an HIV combo than with HIV meds alone. Adding Proleukin didn’t protect them from death or opportunistic infections—although it did raise their CD4 counts. The CD4 cells Proleukin produces might be ineffectual, or the drug may cause immune damage that undercuts the increase in cells. Either way, it’s out of the running as a treatment for HIV.