Spermine restrains innate immune responses by inhibiting M1 macrophage activation via suppression of ornithine decarboxylase and pro-inflammatory cytokine synthesis without perturbing anti-inflammatory TGFβ and IL-10 (Figure 2).113,114 Spermidine also modulates systemic and mucosal adaptive immunity by modulating T cell differentiation.122,123 Clinically, N-acetyl putrescine and N-acetyl spermidine are enriched in allo-hematopoietic stem cell transplantation (HSCT) recipients free from graft versus host disease (GvHD) compared to those with GvHD124 (Table 5). This evidence concerns the gene IL10 and graft versus host disease.