The therapeutic effects of fullerene derivatives on many models of inflammatory disease have been demonstrated. The anti-inflammatory mechanisms of these nanoparticles remain to be elucidated, though their beneficial roles in allergy and autoimmune diseases suggest their suppressive potential in acquired immunity. Here, we evaluated the effects of C-60 pyrrolidine tris-acid (C-60-P) and polyhydroxylated fullerene (C-60(OH)(36)) on the acquired immune response in vitro and in vivo. In vitro, both C-60 derivatives had dose-dependent suppressive effects on T cell receptor-mediated activation of T cells and antibody production by B cells under anti-CD40/IL-4 stimulation, similar to the actions of the antioxidant N-acetylcysteine. In addition, C-60-P suppressed ovalbumin-specific antibody production and ovalbuminspecific T cell responses in vivo, although T cell-independent antibodies responses were not affected by C-60-P. Together, our data suggest that fullerene derivatives can suppress acquired immune responses that require T cells.