EDA and neoplasm: Most likely, a concerted action of ED1+ monocytes, presumably acting as antigen presenting-cells and of primed T cells is necessary for rejection of human GBM xenografts in the rat CNS, since 1) primary GBM xenograft tissue consistently engrafts in T cell compromised nude rats (here, and [5]), but is invariably rejected in T cell sufficient immunocompetent littermates; 2) a tumor-to-host adaptation process occurs in nude rats that leads to a dramatic attenuation in the numbers of host microglia/macrophages.