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Graft versus host disease (GVHD) results from hyper-activation of transplanted lymphocytes against the host antigens. Bone marrow transplantation in humans as well as some cases of blood transfusion and organ transplantation are associated with a strong GVH reaction resulting in GVHD that in many cases may be fatal. We had previously shown that poly-dispersed acidfunctionalized single-walled carbon nanotubes (AF-SWCNTs) specifically target activated T and B lymphocytes and kill them. In the present study, efficacy of AF-SWCNTs to suppress the GVH reaction was tested in the mouse model. Acute GVHD was induced in mice by administering intravenously 30 or 60 million spleen cells from a parental strain (C57bl/6 mouse, MHC haplotype H-2 b ) to host (C57bl/6 x Balb/c) F1 mice (MHC haplotype H-2 b/d ) and waiting for 8-10 days. Chronic GVHD was similarly induced by administration of 30 million parent spleen cells to F1 mice and waiting for a period of 60 days. Our results demonstrate a marked decline in splenomegaly and recovery of spleen T (both CD4 and CD8) and B cells in GVHD mice treated with AF-SWCNTs. AF-SWCNTs treatment also limited T and B cell proliferation by restricting S-phage of cell cycle. Generation of anti-host cytotoxic T cells (CTLs) was also markedly suppressed by AF-SWCNT treatment of acute GVHD mice, and a significant reduction in the generation of anti-host antibodies could also be demonstrated. Taken together, our results suggest that the AF-SWCNTs can be considered as a potential therapeutic agent for treating GVHD.

Graphical abstract

Background AF-SWCNTs are known to have significant effect on the immune function. There is not much information available on the effect of carbon nanotubes (CNTs) on the differentiation of the HSCs. In the present study we have focused on studying the modulatory effects of AF-SWCNTs on the differentiation of HSCs into T & B cells. Methods Single-walled CNTs were acid-functionalized by treating with concentrated sulfuric & nitric acid; thus, tagged with Alexa Fluor 633 to get fluorescent AF-SWCNTs (FAF-SWCNTs). To study internalization, magnetic beads enriched C57bl/6 mouse bone marrow (BM) HSCs (Lin− Sca1+cKit+) were incubated with FAF-SWCNTs & studied using flow cytometry & confocal microscopy. HSCs were cultured with a cocktail of cytokines to induce differentiation to T & B cells, in (+/−) AF-SWCNTs & monitored by live cell imaging. For in vivo ontogenesis study, mice were lethally irradiated (gamma irradiation) & reconstituted using syngeneic BM cells pretreated (+/−) AF-SWCNTs. At different time points, appearance of T & B cells in the spleen was monitored. Results Our results indicate that HSCs internalized significant amounts of FAF-SWCNTs in vitro that remained essentially localized in cytoplasm. Differentiation of cytokines stimulated HSCs to T & B cell was significantly suppressed by AF-SWCNTs. Results of our in vivo experiments indicated that after 17th day of BM transplantation, significant numbers of T & B cells appeared in the reconstituted mouse spleen. However, when AF-SWCNTs pretreated BM cells used to reconstitute irradiated mice, significant decline in both of their percentage & absolute recovery was noted. These results indicate that CNTs may significantly modulate the differentiation of HSCs into lymphocytes.