Roles of tumour localization, second signals and cross priming in cytotoxic T-cell induction

Article Abstract:

Research is presented concerning the response of T-cells to different types of tumors. The action of T-cells in the prevention of tumor cell growth and the occurrence of tumor cell tolerance by T-cells are discussed.

Cell differentiation, Tumors, Letter to the Editor, Cell research, Cytological research, Immune system

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Viral escape by selection of cytotoxic T cell-resistant virus variants in vivo

Article Abstract:

The immune system is successful in protecting the body from viral infection the vast majority of the time. However, some viruses may evade the immune system defenses by a number of different mechanisms. Some viruses invade protected sites, like the brain, where the immune system cannot effectively attack; some viruses down-regulate the cellular expression of both viral antigens and the MHC (major histocompatibility complex) molecules which might present these antigens to the immune system. It is virtually certain that viruses like influenza, against which immunized people are protected by antibodies, can gradually accumulate enough mutations to avoid recognition by these protective antibodies and reinfect the immune population. Researchers have now shown that viruses can also avoid the destruction of infected cells by immune T cells through the selection of new variants. This was demonstrated through the experimental infection of mice with lymphocytic choriomeningitis virus (LCMV). Since the normal repertoire of T cells is so large, it would be difficult to observe the selection of mutant viruses which escape recognition. Therefore, investigators used transgenic mice in which the majority of T cells recognized a single viral antigenic determinant. If a viral variant develops that can escape this immune recognition, it should multiply rapidly and be directly detectable. This is exactly what the researchers found. New variants of LCMV appeared which were altered in the very antigenic determinant used by the T cells for their recognition and destruction. Having evaded this surveillance, the LCMV were free to replicate. Although the experimental conditions were highly artificial, the researchers believe that a similar process might occur during the development of slow, progressive infections such as AIDS. Since HIV, the AIDS virus, does not stimulate the production of protective antibodies, the T cells may be the major barrier to infection. If the rapidly mutating virus can escape this protection, the infection may be free to progress without interruption. (Consumer Summary produced by Reliance Medical Information, Inc.)

Research, Genetic aspects, Virus diseases, Meningitis, Immunogenetics

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Specific cytotoxic T cells eliminate cells producing neutralizing antibodies

Article Abstract:

The selective infection of B cells producing neutralizing antibodies by the lymphocytic choriomeningitis virus (LCMV) causes their elimination by the virus-specific cytotoxic T cells in mice. Neutralizing antibodies are produced much earlier than protective antibodies in response to cytopathic viral infections. However, the opposite is true for infections like LCMV and hepatitis B due to the T cell-induced specific B cell elimination. This delay in the production of neutralizing antibodies may lead to persistent viral infections by non-cytopathic viruses.

Analysis, Cell-mediated cytotoxicity, Cell mediated cytotoxicity, B cells, Antibodies

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