Tuesday, 22 March 2016

Unintelligent Design - Rejuvenating Parasites

Schistosoma mansoni
Stem cell progeny contribute to the schistosome host-parasite interface | eLife

It gets a bit tedious to keep writing about all these examples of mindless stupidity in biological 'design' but my creationist readers love having something to ignore, or in some cases, post abusive comments on to impress Jesus.

So, not wishing to disappoint, here's another one. It is the discovery, published today in eLife, that a particularly nasty flatworm parasite, Schistosoma mansoni, that causes schistosomiasis in tropical parts of the world, has a simple defense to the human immune system that is trying to destroy them.

My Intelligent (sic) Design believing friends tell me that everything in nature was made by magic by the same magic man they believe also wrote the Bible so they believe this Intelligent (sic) Designer made these parasites especially so they could live in our blood and make us sick. The problem is, it then seems to have made a silly mistake, forgotten what it designed them to do, and designed an immune system for humans that would help us get rid of them and stop them making us sick.

The team of scientists from the Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, USA, and the University of Texas Southwestern Medical Center, USA, have discovered that the parasites have a way to overcome the human immune system. Presumably, my ID-believing friends will explain that their Intelligent (sic) Designer has intelligently (sic) redesigned the flatworm to compensate for its earlier mistake in designing the human immune system.

Schistosomes infect more than 200 million of the world's poorest people. These parasites live in the vasculature, producing eggs that spur a variety of chronic, potentially life-threatening, pathologies exacerbated by the long lifespan of schistosomes, that can thrive in the host for decades. How schistosomes maintain their longevity in this immunologically hostile environment is unknown. Here we demonstrate that somatic stem cells in Schistosoma mansoni are biased towards generating a population of cells expressing factors associated exclusively with the schistosome host-parasite interface, a structure called the tegument. We show cells expressing these tegumental factors are short-lived and rapidly turned over. We suggest that stem cell-driven renewal of this tegumental lineage represents an important strategy for parasite survival in the context of the host vasculature.

© 2016, Collins et al. Reprinted under Creative Commons Attribution Licence (CC BY 4.0)

The tegument serves as a barrier between S. mansoni and the bloodstream of its host, which would otherwise be an inhospitable environment for the parasite. This tissue has long been considered an evolutionary innovation for parasitic flatworms to evade their host's immune defenses. Our current findings suggest that stem cells are playing a key role in perpetually renewing it, and we believe this is important for the parasite's ability to survive for decades inside their human host.
James Collins,
Assistant Professor of Pharmacology,
UT Southwestern Medical Center
Quoted in ScienceDaily
The solution was relatively simple. As quickly as the human immune system destroys the surface of the parasite, so the parasite replaces it. In effect, it continually renews its skin.

The mystery is, and one which my creationist friends never seem to explain, usually because they run away or change the subject, or sometimes start shouting abuse and telling me I'm stupid - in fact anything but explain it - is why something supposedly intelligent would have to keep designing workarounds for its earlier workarounds as though it can't think ahead and plan.

To an evolutionary biologist of course, there is no problem to be explained. It is the 'design' of a mindless, unplanned and uncaring natural process - evolution. It is the expected result of a classical evolutionary arms race - exactly what the theory of evolution by natural selection predicts. There is no magic designer, intelligent or manifestly stupid, required in the scientific explanation.

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