Clue found to T cell loss in AIDS

Article Abstract:

Scientists have learned about the AIDS virus (HIV) more rapidly than any virus previously studied. However, despite great gains in knowledge about the virus' molecular structure and genetics, fundamental questions about the biology of the virus remain unanswered. For example, why does HIV kill T cells? The destruction of T cells in the blood is a hallmark of the relentless progression of HIV infection to full-blown AIDS. However, of the T cells destroyed, only about one in 10,000 appear to be actually infected with the virus itself. Why the uninfected cells die remains uncertain, but some possible explanations appear to be gaining the support of experimental evidence. These explanations center on a molecular structure known as a superantigen. Superantigens are molecules that stimulate massive immune responses. Unlike antigens, which stimulate immune reactions only after being broken up and presented to T cells which specifically recognize them as a part of a molecular complex, the superantigen binds to part of the T cell antigen receptor (the beta chain), and stimulates an immune response outside of the normal recognition system. This massive immune stimulation might seem to be a good thing, but the stimulation also results in apoptosis. Apoptosis is also called programmed cell death, and is a natural physiological mechanism for eliminating cells after they are no longer needed. By inducing apoptosis, a superantigen can destroy countless T cells. Bacterial superantigens have been studied in the laboratory, and a superantigen has even been found in a virus that causes an immunodeficiency syndrome in mice. The properties of superantigens would go a long was toward explaining the massive loss of T cells resulting from HIV infection. Indeed, researchers have examined the patterns of T cell loss in AIDS patients and found them to be consistent with the action of a superantigen. However, exactly what aspects of HIV might account for the hypothesized superantigen characteristics remains uncertain. (Consumer Summary produced by Reliance Medical Information, Inc.)

T cells

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Kaposi's sarcoma puzzle begins to yield

Article Abstract:

Kaposi's sarcoma is a common manifestation of AIDS (acquired immunodeficiency syndrome). Indeed, it was one of the very first observations that indicated to medical scientists that something peculiar was happening among gay men. The once obscure cancer is 20,000 times more likely among AIDS patients than in the general population. Although it is clear why AIDS would increase the frequency of some infections, the reasons behind the relationship of AIDS and Kaposi's remain something of a mystery. Evidence has begun to accumulate that AIDS may provide a good environment for the growth of Kaposi's sarcoma by stimulating some cells to produce growth factors. Growth factors are normal substances which, as their name implies, stimulate cell growth. However, slight irregularities in growth factor production may be a key event in the unregulated growth of some tumors. Scientists have found that the tat protein, which is a gene product of the AIDS virus, is a growth factor for Kaposi's sarcoma cells. They believe that the infected T cells produce this factor, which may stimulate the development of the sarcoma. Other scientists have implicated the protein interleukin-6 in a similar role. Are growth factors sufficient to explain the incidence of Kaposi's sarcoma? It appears not. One mysterious aspect of Kaposi's is that it is more common among homosexual men with AIDS than among drug users with AIDS. Some scientists suggest that this implies that Kaposi's sarcoma is the result of an infection with an as-yet-unidentified virus which is sexually transmitted. According to this hypothesis, the AIDS virus and the hypothetical Kaposi's virus are likely to occur in the same group of sexual partners. The Kaposi's virus may infect the cells, and the AIDS virus provides a suitable environment for the cancer to grow and thrive. (Consumer Summary produced by Reliance Medical Information, Inc.)

Laws, regulations and rules, Causes of, Complications and side effects, Growth, Growth (Physiology), Kaposi's sarcoma, editorial

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Chromosome yield new clue to pairing in meiosis

Article Abstract:

Two separate teams of researchers have discovered preliminary evidence that heterochromatin may be responsible for chromosome matching during meiosis. This could yield new clues to the process of disjunction and how errors can result in conditions such as Down's syndrome.

Research, DNA, Chromosomes, Fruit-flies, Meiosis

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