Hydroxyurea exerts an anti‐proliferative effect on T cells but has no direct impact on cellular activation

Summary Hydroxyurea (HU) is a cytostatic drug which has been used as an anti‐HIV agent due mainly to its synergistic activity when combined with certain anti‐retrovirals. In addition, HU might have a beneficial effect on parameters involved in the pathogenesis of HIV infection, such as immune activation. To test this hypothesis, the effect of HU on T cell proliferation and T cell activation, as well as the potential association between these two phenomena, were examined in an in vitro model. HU exerted a dose‐dependent anti‐proliferative effect on T cells, and modulated the expression of different activation markers. In cells exposed to HU, expression of CD25 and CD38 diminished in a dose‐dependent manner, whereas expression of CD69 increased. However, when the expression of these markers was examined separately on proliferating and non‐proliferating lymphocytes, HU did not exert any significant effect. Thus, the effect of HU on T cell activation is not direct and seems to be mediated through its effect on T cell proliferation.