Immunology and Cancer
published: Feb. 21, 2011, recorded: June 2006, views: 4140
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Jianzhu Chen lays out the thorny challenges of harnessing the immune system to fight cancer. He starts with the basics: how the body employs two levels of defense against pathogens: native and adaptive immunity. The latter type of protection specifically interests Chen, because it can recognize and remember “an almost unending number” of specific pathogens, both inside and outside cells.
B cells, produced in the bone marrow, can generate antibodies for clearing out bacteria, and T cells, originating in the thymus, go after viruses and other intracellular threats. They work by identifying an antigen (foreign substance) and expressing receptors -- cell surface proteins -- that bind to those antigens.
Early on, the immune system learns to distinguish between what is self and what is a pathogen. It develops, says Chen, “layers of self-tolerance,” without which the body might launch an assault on itself. But cancers can manipulate this useful feature of the immune system. Some tumors express chemicals, or summon naturally occurring suppressor cells in order to prevent T-cells from attacking them. So, says Chen, to mount an immune response against cancer, says Chen, you “need to induce a response against the self—you have to overcome the built-in tolerance mechanism of the immune system.”
Chen sees evidence of the possibility of overcoming “tumor-induced tolerance.” For instance, some tumors spontaneously shrink, and there’s an accumulation of immune cells at tumor sites. Researchers are focusing on three areas: using antibodies or T cells in cancer therapy; developing a therapeutic vaccine that would induce cancer specific antibodies or T-cells; and designing a vaccine to prevent cancer that would induce the memory of B or T cells for a specific cancer. Much hard work remains: identifying tumor associated antigens, most of which, says Chen, the body sees as “normal self proteins;” and then coming up with T or B cells specifically targeting these tumor associated antigens.
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