Effect of buckminsterfullerenes on cells of the innate and adaptive immune system: an in vitro study with human peripheral blood mononuclear cells

Hanno Bunz, Sandra Plankenhorn, Reinhild Klein

Department of Internal Medicine II, University of Tübingen, Tübingen, Germany

Abstract: C60 nanoparticles, the so-called buckminsterfullerenes, have attracted great attention for medical applications as carriers, enzyme inhibitors or radical scavengers. However, publications evaluating their immunological mechanisms are still rather limited. Therefore, we aimed to analyze systematically the in vitro influence of polyhydroxy-C60 (poly-C60) and N-ethyl-polyamino-C60 (nepo-C60) on peripheral blood mononuclear cells (PBMC) from healthy individuals, angling their effect on proliferation, expression of surface markers, and cytokine production. We isolated PBMC from 20 healthy subjects and incubated them in a first step only with poly-C60 or nepo-C60, and in a second step together with recall antigens (purified protein derivative, tetanus toxoid, bacillus Calmette-Guérin). Proliferation was determined by ³H-thymidine incorporation, activation of PBMC-subpopulations by flow cytometry by measurement of the activation marker CD69, and secretion of T helper cell type 1 (TH1)- (interferon-gamma [IFN-γ], tumor necrosis factor beta [TNF-β]), TH2- (interleukin-5 [IL-5], -13, -10) and macrophage/monocyte-related cytokines (IL-1, IL-6, TNF-α) into the supernatants by enzyme-linked immunosorbent assay. Both fullerenes did not influence T cell reactivity, with no enhanced expression of CD69 and production of T cell cytokines observed, the CD4/CD8 ratio remaining unaffected. In contrast, they significantly enhanced the release of IL-6 and CD69-expression by CD56 positive natural killer cells. PBMC, which had been cultured together with the three recall antigens were not affected by both fullerenes at all. These data indicate that fullerenes do not interact with T cell reactivity but may activate cells of the innate immune system. Furthermore, they seem to act only on ‘naïve’ cells, which have not been prestimulated with recall antigens, there are however, large inter individual differences.

Keywords: buckminsterfullerenes, polyhydroxy-C60, N-ethyl-polyamino-C60, natural killer cells, dendritic cells, T cells, cytokines