Highlights Immune System (continued)
1. T-cells work by interacting with protein complexes on cell surfaces called Major Histocompatibility Complexes (MHCs).
2. MHCs come in two types - MHC class I, which is found on most cell surfaces and MHC class II which is found primarily on B-cell surfaces.
3. If a cell gets infected, it will digest some of the protein of the invading virus (or cell) and "present" the peptide piece by placing it on the MHC I on its surface. Killer T-cells (also called cytotoxic T-cells) will interact with that presented peptide through a T-cell protein called CD-8. When this interaction occurs, the T-cell will release a protein called perforin that will poke a hole in the infected cell. Through the hole in the infected cell, the T-cell will insert enzymes called granzymes that will induce the infected cell to commit suicide.
4. Helper T-cells are important in stimulating B-cells that have bound to an antigen to replicate, thus creating more B-cells with that antigen. This occurs when the helper T-cell recognizes that a B-cell is presenting a peptide from the antigen on it MHC II receptor. The T-cell interacts with the MHC II complex through a T-cell surface protein called CD4. When this happens, the helper T-cell releases molecules that stimulate the B-cell to divide.
5. Use of special antibodies called monoclonal antibodies are used to treat some cancers. Breast cancer commonly has a receptor on it cell surface called HER that is made in too great of a quantity. HER plays a role in signaling the cell to divide when it binds to proteins called growth factors. Too many HER receptors causes too many signals to divide to occur and the cell divides uncontrollably, thus causing a cancer. Monoclonal antibodies are created that bind to a very specific epitope in HER and these are given to patients. The monoclonal antibodies bind to HER, and stop the signaling and can slow or stop the growth of a cancer that arises when HER is overexpressed.
Highlights Environmental Biotechnology
1. Biotechnology for improving the environment is not new. For as long as there have been people, there have been problems with human waste and biotechnology has been brought to bear on this problem.
2. Clean water is an important need for everyone, but it is sobering to note that the water needs for one cow are equal to those of 16 city dwellers.
3. Sewage plants are modern ways of dealing with human waste that are not only very effective at reducing the environmental impact of the waste, but also producing useful products. For example, waste is a rich source of organic matter. This can have uses in fertilizers, in some cases.
4. Another important consideration in decomposing material (which is what is happening wherever bacteria are breaking down biomass, such as in a landfill or a sewage plant) is that this can be used as a source of energy.
5. A class of organisms known as archaebacteria make methane as a byproduct of metabolism. Methane, of course, is the component in natural gas that we burn to release energy. The specific archaebacteria that make methane are known as methanogens.
6. Swamps are places of considerable amounts of decomposition and they are full of methanogen bacteria. It is likely that the stories of "Will of the Wisp" are actually resulting from glowing blobs of methane gas released by these bacteria, particularly on warm summer nights.
7. Methane from decomposition like this could supply 1% of U.S. energy needs.
8. Ethanol is a biofuel arising from action of microbial organisms (bacteria and yeast) under anaerobic conditions (no oxygen). Common nutrients given to feed these bacteria commonly come from corn or sugar cane. These materials, however, are food crops and the result is that people are going hungry so ethanol production can occur.