Fig. 5

Immunoperoxidase staining of microglia in brain sections from mock-vaccinated and vaccinated mice. a The large tumor from a mock-vaccinated mouse occupies the central, lower and right areas in this image. Uninvolved brain is in the upper left quadrant of the image. Brown staining marks microglia in the surrounding brain and in the tumor. The border of the tumor with the surrounding brain is distinct but ragged (magnification ×20). b This photomicrograph from the same mock-vaccinated mouse shows the interface of tumor and adjacent brain. Staining for microglia is present in both. Tumor cells are hyperchromatic and atypical mitoses are present. A thin rim of microglia staining adjacent to tumor cells is visible (magnification ×100). c This photomicrograph shows a much smaller tumor in a vaccinated mouse. Microglia cells are intermingled within the tumor, attached to tumor cells, and are more numerous in surrounding brain. Microglia cells are also more numerous around tumor cells in vaccinated mice compared to mock-vaccinated ones (magnification ×40). d In this photomicrograph from the same vaccinated mouse, numerous microglia cells surround glioblastoma cells, distinguished by their nuclear atypia, pleomorphism, nucleomegaly and nucleoli. Microglia have much smaller nuclei and their cytoplasm is marked by the immunoperoxidase stain (magnification ×200). e In a different vaccinated mouse, microglia surround tumor cells, which are very large and have nucleomegaly with multiple nucleoli. Stained microglia cells are located on the perimeter of the malignant cells (magnification ×400). f This low-power image of a small tumor from a vaccinated mouse shows the concentration of staining within the tumor and the large number of activated microglia in the surrounding neuropil (magnification ×20)