Implantation of dispersed cells into primate brain

Although several experimental therapies such as dopaminergic cell implantation in parkinsonian models and intratumoral placement of lymphokine-activated killer cells require intracerebral deposition of dispersed cell suspensions, a successful technique of needle implantation of cells into primate brain has not been demonstrated. The authors have sought to establish a stereotaxic technique to predictably deposit dispersed cells in primate brain. Human lymphocytes were cultured in recombinant interleukin-2, labeled with sodium 51 chromate (⁵¹Cr), and stereotaxically injected into the frontal white matter of six anesthetized rhesus monkeys. A 10-μl aliguot of cell suspenion (2 x 10⁷ cells/ml)w as deposited 16 mm deep to the dura at 5 min via Hamilton No 22s or 26s needles. Five control aliquots were counted for each injection. Reflux out of the needle track was absorbed on gauze, and the recovered cells were counted. The animals were sacrificed 1 hour after implantation and the brain was removed and sectioned such that the cortex and white matter along the needle track were separate. The tissue sections were then counted. Recovery was expressed as the percentage of total injected radioactivity (cpm) that was present in each brain section. Two additional injected hemispheres were processed for autoradiography and histologiical study. Cell recovery in the brain (mean ± standard deviation) was 87.2% ± 13.9% (3.3% ± 4.9% in cortex and 83.9% ± 15.9% in white matter). The autoradiograms and histological examination showed a dense accumulation of radioactivity (cells) at the target site and minimal radioactivity (cells) in the needle track. Accurate intracerebral deposition of dispersed cells in primates was achieved with the technique described. This knowledge permits reliable stereotaxic implantation of cells into the brains of nonhuman primates and humans for investigation and therapy.