During GVHD, we observed that these cells acquired an activated, inflammatory phenotype, characterized by a transcriptional profile that revealed increased expression of MHC class I and II genes, along with a wide array of chemokine genes (i.e., Ccl2, Ccl3, Ccl4, Ccl5, Ccl7, Ccl12, Cxcl9, and Cxcl10), which function to recruit monocytes, T cells, and other immune cells into the brain. Here, CCL4 is linked to graft versus host disease.