
The mechanism behind the defense action of human immune system in distinguishing between the foreign particles (for e.g. microbes) and the body's own structure is well understood in a research work. Research team at the University of Helsinki, Finland carried out this research.
When a microbe has infected us, the first defense mechanism that attacks it is a protein-based marking and destruction system called complement. It usually suffices that foreign targets are marked as enemy while our own targets are left untouched, so that white blood cells attack only foreign targets like bacteria, viruses and parasites.
Researchers at the Haartman Institute and the Institute of Biotechnology at the University of Helsinki have, as a result of years of dedicated work, been able to show how complement dis-tinguishes foreign structures from our own structures all days before antibodies have a chance to develop. The key to unlocking the problem was when the groups of Sakari Jokiranta and Adrian Goldman in Helsinki, along with David Isenman's group in Canada, were able to solve the structure of two components of the system at atomic resolution. The structure revealed a stunning unexpected arrangement: factor H bound two of the C3bs, which mark foreign targets, in two different ways. Laboratory tests showed that this actually happened: to recognise our own cells, factor H binds not only C3b but also the cell surface at the same. Thus, the system mark only foreign structures for destruction by the white blood cells.
Source: Eurekalert
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