CD4 cell counts are still increasing after seven years of antiretroviral therapy in patients whose baseline CD4 cell count was below 500 cells/mm3 when they started HIV therapy, delegates to the recent Conference on Opportunistic Infections and Retroviruses (CROI) learnt earlier this month. Other research presented to the conference also showed that, to stand the best chances of achieving an increase in CD4 cell count to normal levels, it is necessary to start treatment with a CD4 cell count above 350 cells/mm3, and that patients with ongoing immune activation and a large thymus have smaller gains in CD4 cell count. A small study in the United Kingdom also suggested a possible role for recombinant human growth hormone to 'kick-start' HIV-specific immune responses.