Science Square

  • Issue 84 / November - December 2011



    Immune system at training in the gut

    The Fountain

    1- Immune system at training in the gut
    Microbes, in particular bacteria, are associated with many diseases, being the deadliest pathogens along with viruses. But, this doesn't mean that all bacteria are harmful. Indeed, most bacterial colonies that reside in our gut have mutualistic relationship with humans. Our intestines carry approximately ten times more bacteria than the total number of cells in human body. This vast number of bacteria residing in our intestines are not only harmless, but they are also beneficial for us in many ways, by digesting food to supply energy for the body, by outcompeting the disease-causing bacteria in the intestines, and by producing vitamins and hormones. This study brings a new dimension to our understanding of the interactions between the host immune system with the gut microflora. The main components of immune system are the T cells that can recognize the pathogens. Each T cell recognizes one particular pathogen and distinguishes self-cells from the pathogens. In the thymus, T cells that recognize self-molecules are either eliminated or transformed into a special category of T-cells called regulatory T cells (Tregs), whose job is to maintain tolerance towards self-antigens. Lathrop and colleagues demonstrated for the first time that naïve T cells are developed into Tregs in the gut upon encounter of commensal gut bacteria. What is striking is that these Tregs responded to the bacterial antigens, unlike the thymus originated Tregs that were generated by self-antigen recognition. These data suggest that gut bacteria train host's immune system to be silent against themselves and act only against invading pathogens. Mechanisms involved in distinguishing harmful vs. beneficial bacteria by the immune system may provide new ways of tackling with bacterial diseases.

    2- Cancer meets memory
    Original Article: Odajima, J. et al., Developmental Cell 21, 655 (2011).
    The recent discovery in the field of neuroscience reminded us the phrase "context is everything." A study conducted by the scientists of Dana-Farber Cancer Institute and Harvard Medical School addressed somewhat contradictive observation that why human brain has high levels of cyclin E protein, a well-known culprit in many cancers. Cyclin E protein plays an important role in cell cycle where it helps to regulate the timing and the frequency of cell division in normally growing cells. However, overexpression of cyclin E has been associated with uncontrolled cell growth in various cancer types. It is surprising that the human brain, which has a group of non-dividing cells, also express cyclin E at high levels. The study showed that when cyclin E deficient mice were analyzed, there was a serious defect in the formation of nerve connections as well as the formation of memory. "It is overexpressed in many different cancers, but it also is expressed in high levels in the human brain. We have found that cyclin E is needed for memory formation and is a very important player," said senior author Peter Sicinski, PhD, a cancer biologist at Dana-Farber. The study showed that cyclin E achieves its functions in the brain by binding to Cdk5 enzyme whose activity is associated with Alzheimer's disease. "There is good evidence that hyperactivity of Cdk5 contributes to Alzheimer's disease and inhibiting this enzyme can ameliorate symptoms in animals," said Sicinski. "Manipulating cyclin E levels might be another way to accomplish this," he added.

    3- Designing perfect plastic
    Original Article: Read, D.J. et al., Science 333, 1871 (2011).
    Plastic is used everywhere in our daily lives. Up until now, production of different types of plastic was done by trial and error. Only a small fraction of these trials give rise to a usable product. After ten years of hard work, scientists have now developed a computer program that can predict properties of plastic without actually manufacturing it. The program has two parts. The first part can predict how a specific polymer will flow based on the connections between the macromolecules that make up the polymer. The second part predicts the shape of these macromolecules when they are made at a chemical level. Using this code, one can effectively construct a recipe book for plastic. This will make it possible to design plastic that can better handle a specific job. It will also be possible to make plastic out of renewable materials instead of oil based materials which will be easy to recycle.

    4- The key to long life?
    Original Article: Kim, E.B. et al., Nature (published online before print, 2011).
    Who would want to live a long life at the cost of looking ugly? One type of rodent species, naked mole rat, seems to have said "yes" to this intricate question. While an average rodent, a house mice or a rat living on streets, can live up to 4 years, naked mole rats can live up to 30 years. Mole rats are hairless, buck-toothed and almost blind rodents that are only found in dry sections of the Horn of Africa. They live in underground colonies with a social structure similar to ant colonies. There is a queen rat that chooses to mate with only few males, and rest of the colony takes the big responsibility of maintaining and protecting the colony. Scientists have always been puzzled with the extraordinary life span of these exotic animals and they finally generated the complete gene map of these intriguing animals. A quick look of the genomic map revealed that many genes associated with vision, circadian rhythms, perception of pain and perception of bitter tastes seem to be completely turned-off. Perhaps, these specific modifications allow animals to tolerate harsh living conditions and help them to adapt a lifestyle which lacks so-called the luxuries and expectations of a normal animal. Scientists believe that comprehensive analyses of naked mole's genetic map might shed light on fundamental cellular mechanisms that are disrupted in aging and aging-related diseases.

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