ICOS and graft versus host disease: T cells from GVHD mice had increased expression of Icos, Stat1, Il12rb2, Ly6c2, and Ly6a, indicative of an activated memory phenotype (Supplemental Figure 3C and Supplemental Table 1), whereas the single macrophage cluster from GVHD mice demonstrated increased expression of complement (C1qa and C1qb), chemokine (Ccl5, Cxcl9, and Cxcl10), and S100a genes (S100a8 and S100a11), which all are associated with inflammatory pathways (Supplemental Figure 3D and Supplemental Table 2).