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Impaired cell-mediated immunity in certain patients with nonlymphoid cancer is indicated by depressed skin reactivity to common antigens (1, 2), delayed homograft rejection (3), decreased ability to become sensitized to dinitrofluorobenzene (4) or dinitrochlorobenzene (5, 6), and decreased in vitro lymphocyte responsiveness to the mitogen phytohemagglutinin (7,8). It is not known whether depressed cell-mediated immunity precedes or follows the development of cancer.Tumor-specific antigens and cell-mediated tumor immunity are noted in cases of human cancer. Blood lymphocytes from patients with some neoplasms inhibit tumor cell growth (9, 10) or undergo blast transformation when cultured with autochthonous tumor cells (11). In addition to the cell-mediated responses, the sera of these patients contain antibodies or antigen-antibody complexes (12) that specifically block lymphocyte-tumor cell interaction through a poorly understood phenomenon termed immunologic enhancement (13,14).In the present studies, patients with primary intracranial tumors were found to have depressed cell-mediated immunity. Unlike other patients with solid systemic tumors and impaired delayed hypersensitivity, our patients did not have clinical evidence of metastases, weight loss, or hematologic abnormalities. These patients, then, afforded an unusual opportunity to study host mechanisms responsible for defective cell-mediated immunity.Although delayed hypersensitivity and other cell-mediated responses were depressed, we found evidence of lymphocyte sensitization to tumor antigens. To clarify these apparently paradoxical findings, we evaluated mononuc]ear leukocyte function with the one-way mixed lymphocyte reaction. Cellular reactivity in the absence of patient plasma was normal. Such plasma, however,

ABSTRACT:The planarian is the simplest living animal having a body plan of bilateral symmetry and cephalization. The brain of these free-living flatworms is a biiobed structure with a cortex of nerve cells and a core of nerve fibres including some that decussate to form commissures. Special sensory input from chemoreceptors, photoreceptor cells of primitive eyes, and tactile receptors are integrated to provide motor responses of the entire body, and local reflexes. Many morphological, electrophysiological, and pharmacological features of planarian neurons, as well as synaptic organization, are reminiscent of the vertebrate brain. Multipolar neurons and dendritic spines are rare in higher invertebrates, but are found in the planarian. Several neurotransmitter substances identified in the human brain also occur in the planarian nervous system. The planarian evolved before the divergence of the phylogenetic line leading to vertebrates. This simple worm therefore is suggested as a living example of the early evolution of the vertebrate brain. An extraordinary plasticity and regenerative capacity, and sensitivity to neurotoxins, provide unique opportunities for studying the reorganization of the nervous system after injury. Study of this simple organism may also contribute to a better understanding of the evolution of the human nervous system.

Four stages of development can be recognized in the histogenesis of the human telencephalic choroid plexus. Division into stages is based on alterations of outline of the plexus, characteristic appearance and biochemical content of the epithelial cells, and the components of the stroma. The stages are less distinctive in the myelencephalic and diencephalic plexus where differentiation is accomplished sooner than in the telencephalic plexus. Neuroepithelial-lined tubules are common in the choroid plexus, and are formed by folding of choroidal epithelium into the stroma. Some tubules are large enough to be designated as incipient neuroepithelial (colloid) cysts. Cysts having only connective tissue walls are also present. The choroidal epithelial cells proliferate focally, stratify and desquamate into intervillous clefts, or flow into the stroma by disruption of the epithelial basement membrane or tubular wall. These findings are confirmed by use of serial sections. The size of the developing telencephalic plexus relative to the ventricular system is small at first, then large, occupying almost the entire telencephalon, but gradually decreases during development. Glycogen is prominent i n developing choroidal epithelial cells, but disappears in the mature plexus. Both epithelial and mesenchymal mucin and mucopolysaccharides are identified in the plexus. The paraphysis is re-emphasized as an extraventricular choroid plexus on the basis of a common neuroepithelial origin. It is rudimentary and inconstant in man.We have reviewed in another publication the developmental and comparative anatomy of choroid plexus, ependyma and other derivatives of the primitive neuroepithelium in relation to the development of neuroepithelial (colloid) cysts (Shuangshoti, Roberts and Netsky, '65). It was emphasized in that paper that the paraphysis is an extra-ventricular choroid plexus. Because our data indicated a close relationship between the neuroepithelial cyst and the choroid plexus, we decided to study the histogenesis of the choroid plexus in detail. We described in the same paper the finding of mucin and PAS-reactive materials in neuroepithelial cysts and in fragments of choroid plexus attached to the cysts. Histochemical tests for these substances were therefore conducted on developing choroid plexus to clarify these observations. A few investigators have described the times of appearance of the primordia of telencephalic and myelencephalic plexuses in some mammals as in pig (Weed, '17), guinea pig, rabbit and rat (Cohen and Davies, '38; Strong, '56) but the full histogenesis has not been presented. Kiszely AM. J. ANAT., 118: 283-316.

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