Where do blood-borne cells enter the brain? (99.9)

Abstract

Abstract The blood-brain barrier stops passive entry of proteins, but not living cells. Both tumor cells and leukocytes can enter the brain, and it is attractive to exploit blood-borne leukocytes to attack blood-borne metastases or pathogens. However, more needs to be known about where different cell types enter, lodge, and grow. METHODS. In 6u sections of rat brain, inert beads, blood-borne metastases of marked tumor, and T cells were stained histochemically or by common antibodies. RESULTS. Tumor, T cells, and inert beads can all enter vessels of the brain proper, choroid plexus (within the ventricles), and meninges. However, the relative importance varies with the cell type.Metastases in the brain proper were common for one tumor line, and rare for the other. Both lines metastasized to the choroid plexus.In contrast, the choroid plexus was not, in general, a favored site of T cell entry. T cells were more likely to enter at cerebral vessels.When T cells did accumulate in the ventricles, they were most concentrated in the narrow foramen of Monro. DISCUSSION. The traffic patterns of other populations (T cell subsets, B cells, monocytes) must now be compared. In seeking to exploit blood-borne leukocytes against blood-borne tumor or pathogens, the optimal responding cell type may vary with the target site.