Dealing with Big idea 1, which states the process of evolution drives the diversity and unity of life, consider pages 12-22 in chapter 1 of Survival of the Sickest. If iron causes increases in infections in general, why hasn't hemochromatosis become more prevalent among society today? If hemochromatosis can be monitored, why isn't it the trait being selected for in natural selection? What are the advantages to having hemochromatosis? What are some disadvantages? For those without hemochromatosis, what can be done to prevent the infections that those with hemochromatosis don't have to deal with?
(Posted by Lindsay Pontello, lpontel4@students.d125.org)
Hemochromatosis is a hereditary disease in which the body has an unregulated absorption of iron, even when there is already a sufficient amount of the element floating in the bloodstream. Then, this excess amount of iron deposits itself throughout the body in unneeded places as it travels through the bloodstream and in the process damages the major organs of the body.
ReplyDeleteA disadvantage to having hemochromatosis is that, while all life on earth needs iron to survive, infectious agents need iron to survive as well. Actually, “parasites hunt us for our iron; cancer cells thrive on our iron” (6). Thus, hemochromatosis patients who have a loaded supply of iron are essentially inviting all sorts of prokaryotic organisms (e.g. bacteria, fungi, protozoa) to invade their bodies - where an access to iron allows them to grow rapidly. Luckily enough, during the immune system’s acute phase response (which is activated at the onset of illness), biological invaders’ access to iron is limited, thus hindering them to feed on this element and multiply at an uncontrollable rate. But while the iron defense system is activated during times of illness, some prokaryotic invaders still are able to locate sources of iron throughout the body and feed on them, due to the loaded supply of the element present throughout the body of hemochromatosis patients.
On the other hand, a benefit to having hemochromatosis is that those with this disease never experience iron deficiencies. Iron is very important for the survival of all forms of life. It is responsible for carrying oxygen from the lungs through the bloodstream, and it is released wherever it is needed along the way. In addition, iron is an integral component of the enzymes of the body that help to detoxify poisons and convert sugars into energy. In fact, the importance of having a sufficient amount of iron in the body is exemplified because “iron-poor diets [...] are the most common cause of anemia, a lack of red blood cells that can cause fatigue, shortness of breath, and even heart failure” (4). Because the risk of having an iron-poor diet is not a concern for hemochromatosis patients, hemochromatosis serves as a benefit in that respect. Another benefit to having hemochromatosis is that the macrophages in the immune systems of those with the disease lack iron. As stated previously, the iron-locking response of the body at the onset of illness allows the body to isolate infectious agents. Therefore, infectious agents never make it to the macrophages of the immune system in patients with hemochromatosis and as a result cannot feed and multiply. On the other hand, nonhemochromatic people (whose macrophages have lots of iron) invite infectious agents to help protect the body and in the process give them access to iron which allows them to feed and multiply.
In fact, the bubonic plague was “the direct result of the bacteria’s subversion of the body’s immune system for its own purposes” (13). Thus, because hemochromatosis patients have an iron defense system in place that kicks in when illness is detected that prevent biological invaders from feeding on their abundant supply of iron and then multiplying uncontrollably, hemochromatosis has been selected for in natural selection. Those without hemochromatosis basically give biological invaders a free pass into their macrophages, which contain plenty of iron, and allow them to grow and become dangerous as they travel throughout the body.
(Tina Moazezi, tmoazez4@students.d125.org)