The activation of T helper (Th) lymphocytes is necessary for the adaptive immune response as they contribute to the stimulation of B cells (for the secretion of antibodies) and macrophages (for phagocytosis and destruction of pathogens) and are necessary for cytotoxic T-cell activation to kill infected target cells. For these issues, Th lymphocytes must be converted into Th effector cells after their stimulation through their surface receptors TCR/CD3 (by binding to peptide-major histocompatibility complex localized on antigen-presenting cells) and the CD4 co-receptor. After stimulation, Th cells proliferate and differentiate into subpopulations, like Th1, Th2 or Th17, with different functions during the adaptative immune response. Due to the central role of the activation of Th lymphocytes for an accurate adaptative immune response and considering recent preclinical advances in the use of nanomaterials to enhance T-cell therapy, we evaluated in vitro the effects of graphene oxide (GO) and two types of reduced GO (rGO15 and rGO30) nanostructures on the Th2 lymphocyte cell line SR.D10. This cell line offers the possibility of studying their activation threshold by employing soluble antibodies against TCR/CD3 and against CD4, as well as the simultaneous activation of these two receptors. In the present study, the effects of GO, rGO15 and rGO30 on the activation/proliferation rate of these Th2 lymphocytes have been analyzed by studying cell viability, cell cycle phases, intracellular content of reactive oxygen species (ROS) and cytokine secretion. High lymphocyte viability values were obtained after treatment with these nanostructures, as well as increased proliferation in the presence of rGOs. Moreover, rGO15 treatment decreased the intracellular ROS content of Th2 cells in all stimulated conditions. The analysis of these parameters showed that the presence of these GO and rGO nanostructures did not alter the response of Th2 lymphocytes.