Elevated HLA-E levels in human glioblastomas but not in grade I to III astrocytomas correlate with infiltrating CD8+ cells.

HLA-E is a ligand for the immune-inhibitory NKG2A receptor expressed on NK and T cells. To investigate HLA-E expression and immune cell infiltration in human astrocytic tumors in vivo, we analyzed normal CNS controls and astrocytomas of all WHO grades by immunohistochemistry. Both, CD8(+) immune cell infiltration and HLA-E expression were significantly higher in astrocytic tumors than in normal brain. Further, HLA-E expression levels and immune cell infiltration were significantly correlated in WHO grade IV glioblastomas. Thus, HLA-E overexpression in glioblastomas may be triggered by T and NK cell infiltration.