Neuroblastoma is a type of cancer that most often affects children. Neuroblastoma occurs when immature nerve cells called neuroblasts become abnormal and multiply uncontrollably to form a tumor. Most commonly, the tumor originates in the nerve tissue of the adrenal gland located above each kidney. Other common sites for tumors to form include the nerve tissue in the abdomen, chest, neck, or pelvis. Neuroblastoma can spread (metastasize) to other parts of the body such as the bones, liver, or skin.

Neuroblastoma

Biosynthesis of HLA class I antigens has been studied in a variant B-LCLxT-LCL hybrid, 174XCEM.T2. This cell line encodes HLA-A2 and -B5, but expresses only small amounts of A2 antigen and undetectable B5 antigen at the cell surface due to a mutation inactivating a trans-acting regulatory gene encoded within the class II region of the human major histocompatibility complex. Northern blot analysis with HLA-A- and HLA-B-specific probes shows that 174XCEM.T2 synthesizes quantities of A and B locus mRNA comparable with its class I antigen-positive parent cell line. Immune precipitation studies indicate that 174XCEM.T2 synthesizes normal HLA heavy chains and beta 2-microglobulin which fail to form dimers. The heavy chains are N-glycosylated normally, but processing of the glycan to the complex form does not occur. In addition, free heavy chains in this cell line are not phosphorylated. Thus, the majority of class I heavy chains in 174XCEM.T2 do not combine with beta 2-microglobulin, and are not processed or transported to the cell surface. As both subunits are synthesized in normal amounts, we propose that an additional molecule absent from 174XCEM.T2 and encoded by an HLA-linked gene is necessary for efficient assembly of class I antigen subunits.

Impaired assembly and transport of HLA-A and -B antigens in a mutant TxB cell hybrid.

We have found markedly deficient expression of the class I major histocompatibility antigens HLA-A,B,C and beta 2m on human small-cell lung cancer (SCLC) lines and fresh tumor samples. The deficit of HLA-A,B,C and beta 2-microglobulin (beta 2m) antigen expression was demonstrated with both radiobinding assays and indirect immunofluorescence assays. Immunoprecipitation of metabolically labeled cells with antibodies to class I antigens showed most SCLC lines to have synthesized almost no beta 2m and HLA-A,B,C proteins. Northern blot analysis, using human HLA-A,B, and beta 2m cDNA probes, showed that almost all SCLC lines tested had markedly decreased amounts of HLA and beta 2m mRNA, but both gene products could be induced with interferon treatment of SCLC lines. We conclude that human SCLC, in contrast to other lung cancer types, is characterized by greatly reduced transcription of HLA-A,B,C and beta 2m genes, which suggests the existence of a mechanism for evading the host immune response to the tumor and of an E1a-like product in this type of tumor cell.

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Markedly decreased expression of class I histocompatibility antigens, protein, and mRNA in human small-cell lung cancer.

Research has long supported the view that the brain is immunologically privileged, in part because normal, uninfected neurons were not thought to express major histocompatibility complex (MHC) class I molecules. Recently, however, it has been shown that neurons normally express MHC class I molecules in vivo. Furthermore, accumulating evidence indicates that neuronal MHC class I does not simply function in an immune capacity, but is also crucial for normal brain development, neuronal differentiation, synaptic plasticity and even behaviour. These findings point to new directions for research, and imply that immune proteins could be involved in the origin and expression of neurological disorders.

Immune signalling in neural development, synaptic plasticity and disease.

https://www.cell.com/cell/pdf/0092-8674(86)90509-X.pdf

N-myc amplification causes down-modulation of MHC class I antigen expression in neuroblastoma

Monoclonal antibodies to beta 2-microglobulin (beta 2m), and to the native two-chain molecule, were used to assess the expression of the HLA-A, B, C molecules on human neuroblastoma-derived cell lines. In radioimmuno-, cytotoxic, and microscopic assays, employing fresh and fixed cells, neuroblastoma cells show at best weak activity as compared to glial or lymphoid cells. In binding inhibition assays, neuroblastoma extracts were 200- to 1800-fold less efficient in inhibiting the antibodies than were glial or lymphoid extracts. Immunoprecipitation and SDS-PAGE analysis confirmed that a beta m-like chain is synthesized by the neuroblastoma cells, but the HLA chain could not be visualized by this technique. HLA-A, B, C and beta 2m levels are known to vary among tissues and cell lines. Yet the magnitude of the differences between the neuroblastoma and lymphoid lines is much greater than the reported differences in expression between some of these same lymphoid lines and many other nonlymphoid malignant or nonmalignant cell types. Metastatic neuroblastoma tumor in bone marrow also showed weak HLA-A, B, C activity, with the cells appearing negative in microscopic assays. Possible clinical implications are discussed.

Striking paucity of HLA-A, B, C and beta 2-microglobulin on human neuroblastoma cell lines.

Ten solid neuroblastoma tumors were examined for beta 2-microglobulin (beta 2-m) and HLA-class I expression in an immunocytochemical assay. Blood vessel endothelium and a small population of cells (less than 6% of small round cells) were consistently stained in frozen sections of each tumor. No beta 2-m or HLA-class I reactivity was detected in the remainder (greater than 94%) of the small round cells in each tumor. The localization of most of the positive cells near stromal tissue and blood vessels suggests that most of these cells may be of non-tumor origin. The patients from which the tumors were taken varied in degree of disease involvement, yet no differences with respect to beta 2-m and HLA-class I expression were found among the tumors. A procedure for visualizing beta 2-m and HLA-class I molecules in formaldehyde-fixed, paraffin-embedded tissue is described. This confirmed the results in frozen sections. These findings extend previous reports of weak beta 2-m and HLA-class I levels in cells of neuronal origin. The clinical implications are discussed.

HLA Class I and β2-Microglobulin Expression in Frozen and Formaldehyde-fixed Paraffin Sections of Neuroblastoma Tumors

Previous work indicates that the weak expression in neural tissues of beta 2-microglobulin (beta 2-m) and major histocompatibility complex (MHC) class I gene products can be increased experimentally. Physiologic conditions in which greater neural MHC expression occurs are not well defined. Here we have asked whether protection from blood-borne antigens afforded by the blood-brain barrier is related to the lack of MHC expression. A rabbit antiserum raised against purified mouse beta 2-m was used in an immunocytochemical assay. The serum reacted strongly with lymphoid tissues and was inhibited by purified beta 2-m. No beta 2-m was detected in neurons or glia in any brain area examined. A barrier-free region, the area postrema, showed the same lack of neural cell staining. Blood vessel walls in the same sections were beta 2-m+. It is unlikely that these staining patterns are due to cell type-specific beta 2-m degradation, since frozen and formaldehyde-perfused, paraffin-embedded preparations gave similar results. Failure to detect beta 2-m in the area postrema suggests that passive exposure to environmental antigens, immunomodulators, or immunocompetent cells is not sufficient to induce neural class I expression. Rather, if increased expression of beta 2-m and class I occurs in vivo, additional stimulus is required.

Expression of mouse beta 2-microglobulin in frozen and formaldehyde-fixed central nervous tissues: comparison of tissue behind the blood-brain barrier and tissue in a barrier-free region.

HLA-A,B,C and beta 2-microglobulin are expressed weakly by human cells of neuronal origin, but can be induced in neuroblastoma cell lines by interferon.

The olfactory neuroepithelium is unique in adult vertebrates in that bipolar sensory neurons are constantly dying and being replaced. The sensory neurons are also unusual because they are directly exposed to the external environment via their dendritic processes in the nasal cavity. Surveillance of this tissue by major histocompatibility complex (MHC) class I-restricted cytotoxic T cells would presumably serve as an important means of defense against foreign pathogens. Although adult brain shows a lack of class I molecules, it has not been reported if either proliferating neurons or sensory neurons in olfactory neuroepithelium also lack class I. To examine olfactory neuroepithelium, an antiserum against beta 2-microglobulin (beta 2-m), the invariant light chain associated with all class I molecules, was employed as a general probe in an immunocytochemical assay. beta 2-m was detected in columnar respiratory epithelium, blood vessel walls, and a small population of interstitial cells in the lamina propria, but no cell in the olfactory neuroepithelium stained for beta 2-m. Parallel patterns were obtained in the vomeronasal organ. These results suggest that lack of beta 2-m, and presumably class I, may be a general phenotype of neuronal cells regardless of their mitotic state or exposure to environmental antigens.

J P Whelan

Papers

Striking paucity of HLA-A, B, C and beta 2-microglobulin on human neuroblastoma cell lines.

HLA Class I and β2-Microglobulin Expression in Frozen and Formaldehyde-fixed Paraffin Sections of Neuroblastoma Tumors

Expression of mouse beta 2-microglobulin in frozen and formaldehyde-fixed central nervous tissues: comparison of tissue behind the blood-brain barrier and tissue in a barrier-free region.

HLA-A,B,C and beta 2-microglobulin are expressed weakly by human cells of neuronal origin, but can be induced in neuroblastoma cell lines by interferon.

Distribution of beta 2-microglobulin in olfactory epithelium: a proliferating neuroepithelium not protected by a blood-tissue barrier.