Studies on "brain-specific" proteins in aqueous extracts of brain tissue

Immunological and biochemical strategies for the identification of brain tumor-associated antigens

Various strategies have been used to identify and characterize the antigens associated with human brain tumors. These approaches have included the raising of polyclonal and monoclonal antibodies against tumor antigens and, more recently, efforts toward the direct biochemical identification of such proteins. This review summarizes the progress made in this area, suggests reasons for the broad antigenic cross-reactivity and heterogeneity revealed by these studies, and proposes additional methods for deciphering the complex antigenic composition of human brain tumors.

Invited review. Nervous system antigens

Some of the better characterized proteins (markers) of the nervous system are described. The availability of specific antibodies to these markers has allowed the localization and assay of the proteins in tissue and biological fluids. There is some evidence that autosensitization may occur. Clinical application of these markers includes the evaluation and prognostic significance after stroke and head injury. The diagnostic histopathological use of the markers in the investigation of various tumours is summarized.

Immunoelectron microscopy of alpha 2-glycoprotein. An astrocyte-specific antigen

The cellular and fine structural localization of the soluble brain-specific acidic alpha 2-glycoprotein was investigated using the indirect immunohistochemical method. The electron microscope was used to unambiguously identify cells containing the antigen. A single type of cell, the astrocyte, was found to be labelled with specific antisera directed against alpha 2-glycoprotein. Immunoperoxidase reaction product was found in astrocyte perikarya, their processes and perivascular end feet. It was found to be apparently associated with the cytoplasmic surface of mitochondria, reticular membranes and the plasma membrane. No specific labelling of neurones, oligodendrocytes, myelin or capillary endothelial cells was observed. The data is discussed in relation to the immunological properties of alpha 2-glycoprotein already reported.

Cellular localization of the brain specific alpha 2-glycoprotein in rat cerebellum: an immunohistological study

The cellular localization of the brain-specific, soluble, acidic alpha 2-glycoprotein was studied in rat cerebellum by using the immunoperoxidase technique at the light-and electron-microscopy levels with monospecific immune serum directed against this glycoprotein. Only astrocytes, their processes, and their end feet (subpial or perivascular) contained heavy immunoperoxidase reaction product. Cerebellar neurones, oligodendrocytes, myelin and blood vessel endothelia did not stain. Thus it appears that alpha 2-glycoprotein is an astrocyte marker.

Definition of cellular immune responses to brain antigens in human head trauma

Cellular immune responses to brain antigens in patients with head injury were studied by applying the leukocyte adherence inhibition (LAI) assay. The investigation was conducted in three phases. 1) In the initial phase, evaluation of a series of 22 test and 25 control cases obtained at random during a 2- to 6-week time frame following a traumatic event indicated significant non-adherence of leukocytes (NAL) in 77% of the test group and 20% of the control group in the presence of brain antigen. 2) In a second phase, larger test population was divided into four groups of different posttraumatic intervals. This study measured NAL in the presence of normal heart of normal brain antigen. Assays revealed an initial significant NAL in the presence of both antigens; however, after the first week following injury the majority of cases manifested significant NAL only with brain antigen. These values of NAL persisted over a 6- to 8-week period. 3) As a final phase of investigation, analysis of a sequential series of assays in 12 patients over a 90-day period indicated significant NAL in the presence of brain antigen within the first week of injury, this was followed by a drop in NAL in most of the cases. Studies at 7 to 60 days posttrauma demonstrated significant NAL with brain antigen alone, with a subsequent drop by 90 days. These observations are interpreted to represent sensitization of leukocyte subgroups to brain proteins that are immunologically recognized following the traumatic event.

Glia-specific antigen in the intracranial tumors. Immunofluorescence study

26 gliomas and 14 non-glial tumors were examined for the presence of nervous system specific antigen (CGSA) to assess the antigenic properties of neoplastic tissue in relation to histogenesis and degree of differentiation of tumors. Double layer immunofluorescence (IMF) technique was used for the cellular localization of the antigen. CGSA was found in the cytoplasm of normal, reactive and neoplastic neuroglial cells. Well differentiated astrocytomas showed the strongest IMF reactions and largest number of IMF-positive cells. Tumors with histological signs of anaplasia displayed foci of IMF-negative cells irregularly distributed in the sections. There were no completely negative astrocytomas owing to a marked affinity of the specific astisera to the astrocytic cell line. In the oligodendrogliomas a smaller amount of the antigen was found than in the astrocytomas. Histological evidence of malignancy in these tumors was accompanied by strikingly small number of positive cells and weaker IMF reactions as compared to the well differentiated oligodendrogliomas. Anaplastic gliomas showed only traces of CGSA and non-glial tumors were entirely negative. The results suggest a deficiency of normal antigenic material in the neoplastic glia, particularly of oligodendrogliomas and anaplastic gliomas.

S-100 in the central nervous system of rat, rabbit and guinea pig during postnatal development

The accumulation of the brain-specific S-100 protein has been studied during postnatal development of rat, rabbit and guinea pig quantitatively, using immunoelectrophoresis, and qualitatively, by immunoelectron microscopy. Newborn guinea pigs show high levels of S-100. The distribution was similar to that of adult animals with an enrichment of S-100 to the postsynaptic membranes and to the astrocytic filaments. The neuronal plasma membranes as well as the neuronal nuclear membranes, astrocytic and oligodendroglial plasma membranes, also showed a specific activity for S-100. The amount of S-100 increased linearly from birth until the 3rd and 4th postnatal week of rabbit and rat, respectively. During the 2nd and 3rd week rabbit and rat nervous systems showed an accumulation of S-100, especially in the postsynaptic membranes and in the astrocytic filaments. In this study we present evidence that the S-100 protein quantitatively and ultrastructurally appears according to a pattern which parallels the muturation of brain, showing adult characteristics already at birth in early developing brains (guinea pig) and a change towards adult pattern after birth in late developing brains (rat and rabbit). In the latter two species change towards an adult S-100 distribution pattern proceeds during the postnatal period concomitant with the enzymatic and electrophysiogical maturation of the brain.

Immunoelectrophoretic determination of brain-specific antigens in bulk-prepared neuronal and glial cells

The relative amounts of brain-specific antigens, S-100, glial fibrillary acidic protein (GFA), 14.3.2, synaptin C1, D1, D2 and D3 were determined by crossed immunoelectrophoresis in bulk-prepared neuronal, glial and synaptosomal fractions from 35-day-old rat brains. Little enrichment was ontained for any antigen in the neuronal perikaryal fraction. The glial fraction showed a 3.5-fold enrichment in GFA but had levels similar to whole brain with respect to S-100. Synaptosomes were somewhat enriched in the synaptin C1 protein, but did not differ markedly from whole brain with respect to the most antigens. The extent of cross-contamination in the various fractions could be judged only tentatively, partly due to differences in extractability of the proteins.

Cellular and subcellular distribution of the S-100 protein in rabbit and rat central nervous system

The cellular and subcellular distribution of the S-100 protein in rabbit and rat central nervous system was studied both quantitatively and qualitatively. Microcomplement fixation estimations on bulk-prepared neuronal and glial cells showed at least five to six times higher amounts of water-soluble S-100 in glial cell-enriched fractions as compared to fractions enriched in neuronal perikarya. Nerve cell fractions contained a higher percent of tissue-bound S-100 protein. High levels of S-100 protein were found in mitochondria and soluble protein fractions. Immunoelectron microscope investigations demonstrated S-100 protein in neuronal structures, such as the postsynaptic membrane and part of the plasma membrane. Among glial cells the astrocytic filaments contained high levels of S-100 protein. S-100 was also found in most subcellular membranes of astrocytes and oligodendrocytes.

Immunological differential diagnosis of human brain tumours

Results of immunological experiments with various human brain tumours show differences between astrocytoma and glioblastoma multiforme when brain-specific alpha2-glycoprotein is used as an immunological marker. On this basis a tentative model of cytogenesis and oncogenic transformation of glial cells was presented. Morphological resemblances between the brain-specific alpha2-glycoprotein immuno-precipitation lines obtained from astrocytoma cells and from normal cerebral white matter treated with neuraminidase are discussed in relation to experimental and clinical studies of tumour cells treated with neuraminidase.

S100 brain protein: correlation with behavior

The brain-specific acidic protein, S100, in the pyramidal nerve cells of the hippocampus was investigated as a possible correlate to learning during transfer of handedness in rats. The amount of S100 increased during training. Intraventricular injection of antiserum against the S100 protein during the course of training prevented the rats from further increases in learned behavior but did not affect motor function in the animals. Antibodies against the S100 protein could be localized after injection by immunofluorescence, in hippocampal structures, penetrating presumably through slight ependymal lesions caused by the injection. By contrast, control animals subjected to the same training and injected with S100 antiserum that had been absorbed with S100 protein or with other antisera against gamma-globulins showed no decrease in their ability to learn. The conclusion is that the brain-specific protein, S100, is linked to the learning process, at least within the training used.