In Western countries, atopic diseases – eczema, asthma, and rhinoconjunctivitis – have been on the rise for decades. However, children raised on traditional farms are protected from childhood atopic diseases – in general, they do not develop sensitization to common allergens, as for example grass and birch pollen. The timing and duration of exposure to the farming environment seems to play a critical role in decreasing the risk of developing respiratory allergies, with the most beneficial effects seen in people exposed before birth and continuously thereafter.
Now, results from a study titled “Become a farmer and avoid new allergic sensitization: Adult farming exposures protect against new-onset atopic sensitization” show that the positive effects induced by growing up on farms are also seen in adults who move to farming areas – these adults experience a considerable reduction in symptoms of hypersensitivity and allergy. Although the study does not identify specific factors responsible for the beneficial effect of farming, it emphasizes that “working on a farm has a protective effect against ongoing or newly developing sensitization to common allergens, independent of childhood farm exposure.”
What are potential factors at the basis of the beneficial effects associated with farming? A previous study carried out in an animal model shows that growing up on a farm directly influences the regulation of the immune system and decreases sensitivity to food proteins. This effect seems to depend on an increased number of regulatory T-lymphocytes, the cells that damp down the immune response.
Results from two additional studies indicate that children living on farms are exposed to a wider range of microbes than children living in the same areas (but not on farms) – the investigators conclude that such exposure explains why asthma and atopy are not that common in children growing up in a farming environment.
All together, one of the factors responsible for the beneficial effects of farming is likely to involve the changing relationship between microbes and our immune system. City dwellers no longer encounter the large variety of microbes and parasites that co-evolved with us since the dawn of humanity. These microbes and parasites shaped our immune system in a beneficial way – when they go missing, some components of our immune system may get out of order and become over-reactive.
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This is quite an interesting find! I believe that the improvement in health of these people isn’t due to farming in itself, but to the quality (or purity) of the air that surrounds them in these farm lands. Because cities tend to have air polluted with allergens (chemical proteins, toxins, and pathogens) people living in such areas have immune systems that are constantly at work. These allergens stimulate the production of immunoglobulin E, which is responsible for not only defense against protozoan parasites, but also in controlling allergens. With recruitment of Ig E in the fight against these allergens comes the lovely symptoms of allergies (ie. inflammation). However, many of these allergens don’t exist (or are in minimal amounts) in the fresh air of farm lands, thus, there is no stimulation of the immune system; which would mean no allergies.
References:
Immunoglobulin E
I think you misunderstood the article a bit. The article was stating that individuals raised on farms have a better developed immune system, due to living on a farm and exposure to a variety of animals that possess all kinds of pathogens. As opposed to individuals who didn’t live or grow up on a farm, their immune system wouldn’t be as developed as people who lived on farms due to their lack of exposure to a variety of pathogens. However you make a valid point about the pollutants in city air as compared to air surrounding farm lands.
To elaborate more on your reply, when living on farms, the immune system has the opportunity to interact with microbes in which it has evolved to combat. Evolution has allowed for the immune response to microbes found on farms not be so “hyper” compared to microbes found in cities. This is why there isn’t a hypersensitivity to farm microbes. However, when the immune system interacts with microbes found in cities, the response is hyper because the immune system did not evolve to combat the city microbes. At least, not yet.
What I’m trying to say is that the immune systems of those living on farms is technically not “better” than those living in cities.
The claim is not that farming protects against allergies, but that the changing relationship between microbes and our immune system does….. However, the point you make – cleaner air – is reasonable. On the other hand, the allergens considered here are not those that you mention (chemicals, toxins, pathogens) but things like grass and birch pollen. Plus, pathogens are not allergens.
The relationship between humans and microbes has and probably always will be the same. The claim is that farm raising an individual does protect them from common allergens as the exposure helps to reduce the immune response normally encountered. The reduced response leads to the reduction of allergies.
Regulatory T-Lymphocytes are a part of the immune system that supresses the immune response of other cells. It is also suggested that these regulatory t-lymphocytes can treat autoimmune disease and cancer. With this being said if it is shown that on farms, in animal models, that the regulatory t-lymphocytes are increased then this could account for individuals on the farms being protected from the few diseases mentioned. If there is an up regulation of regulatory t lymphocytes then this could keep the immune system “on its toes” so to speak. This would keep their immune systems alert and ready. Also, being exposed to a variety of microorganisms/pathogens at an early age helps the immune system build up and helps with the memory part of the adaptive immune system.
First you say that regulatory T lymphocytes suppress the immune response, but then you say that if they are up-regulated the immune system is alert and ready. Please clarify the concept you’re trying to convey.
Alright let me clarify, I did say that a little confusing. These Regulatory T Lymphocytes are part of the immune system that suppress other cells in the immune system after they have completed the job they were called up to do. This helps our body stay in check, without over loading ourselves when there is no need to have an overload. If these cells are up regulated this might be why they say-“working on a farm has a protective effect against ongoing or newly developing sensitization to common allergens”. If these cells are up regulated then there would be more suppression on cells in the immune system. But does this mean that our immune system will be suppressed do to this, or does this mean our immune response will work more efficiently by controlling the problems and moving on without a huge ordeal? These cells keep the body from overreacting. Even though you don’t see there job being done they are one of the underlying factors in controlling an immune response by having “control” over other cells.
This article resonates with me! I was born in NYC and practically raised in Atlanta, two very populated cities. My boyfriend was born and raised in Guyana, South America, a fairly rural environment. He always talks about how he drank muddy water straight from the rivers without boiling it or anything and he never got sick. I would always cringe my face in disgust while he tells me I would never survive in Guyana. He also tells me that he never used to get sick until he came to America. I believe our immune systems are still trying to cope with the industrialized environments. In addition, industry is constantly changing and releasing other chemicals and toxins as byproducts. Our immune system takes time to evolve and it cannot catch up to the ever changing industrial environment.
You bring up a valid point about how our immune systems are still trying to cope with the industrialized changes that we are placing on it. My grandparents tell stories about how they never got sick or never heard of so diseases affecting people until recently. I took an evolutionary biology class and we talked about myopia or near sightedness and how the environment played such a huge role in spreading the frequency of the defect. We also discussed how it did not exist in such high numbers until recently when computers and cell phones became popular. Researchers did an experiment with the Inuit and saw that the older adults who did not attend school or did not have to read regularly didn’t have a high frequency of myopia among themselves but the younger children did because they were reading, attending school, and using electronics. The information that I just explained wasn’t necessarily immune related but it does show how environment does affect the body and how disease can develop or become more prevalent due to a change in environment. The immune system changes with the environment.
I believe that the reason your boyfriend could drink “muddy water straight from the river without boiling it or anything” and you cannot without getting sick is not because he was not from an industrialized country, but probably because of the composition of the microbes in his gut. Everyone has bacteria in their intestines that helps digest food and prevents the attachment of potentially pathogenic bacteria, but the composition of the bacteria is different from person to person and normally changes due to location and diet. I believe that the bacteria in the river is not so different than the bacteria that he already has harboring in his gut, so it does not effect him so much. When I go back overseas, my friends eat from the street vendors and are fine while I get very sick whenever I do that. I think the second reason why your boyfriend does not get sick when he drinks water straight from the river without boiling it is because the immune system of the people living there is different than the immune system of someone living somewhere else. The immune system is constantly adapting, and if the people living there can survive while ingesting all the microbes from the river, then they must have built an immunity to those microbes. Mothers pass on some of their immunity onto their children. Especially when they breastfeed, mothers pass on IgA antibodies to their children, which protects against pathogens associated with the mucosal areas, like the intestine. This immunity passed on by the mother is usually sufficient until the children build their own memory lymphocytes against the pathogens and thus have their own immunity. This is also why you do not get sick living in an industrialized country but your boyfriend does; you have built an immunity to the pathogens living here, and your gut bacteria have adapted to the environment here as well, while your boyfriend has built an immunity to the pathogens living in his home country but has not been exposed to the different pathogens here.
Sometimes we sit and wonder how lucky we are that we live in industrialized countries where we don’t get sick because we are so protected. What does protected mean and what are we protected from? Yes we may have an advantage from diseases like malaria and chickenpox but we also have some disadvantages like allergies and autoimmunity. Our immune system is a very complex and smart system that is constantly working on trying to keep us protected. Sometimes it makes mistakes and starts recognizing self-antigens as foreign, mainly because it was not exposed to it during its selection in the primary lymphocytes. The body starts targeting the self-antigens as foreign and starts inflammation. However, the body works on trying to eliminate the antigen, but if the antigen is never eliminated due to it being a self-antigen, then that leads to autoimmunity. In the case of allergies, the body starts recognizing pollen and some other proteins on cell surface as foreign and starts a robust immune response. However, people that are near farms are exposed to parasitic infections therefore, more pathogens, and have immune responses to these pathogens that are good for the body in eliminating them. The body helps fight of the infection and makes a great number of memory cells that circulate the body forever and are readily available upon a second exposure to such pathogens. The people living in industrialized nations are not exposed to such pathogens and so, their bodies readily start attacking harmless pathogens that are due to food and pollen. We can be thankful for our immune system in protecting us constantly from these microbes.
I think you made a very valid point, and that is what the article was trying to say. The immune system is a busy body, and if it is not kept busy with pathogens, it will look for something to induce an immune response against. Usually when the immune system starts looking for pathogens, it starts recognizing self antigens or common allergens against which it will make an immune response, and thus lead to autoimmunity.
In my immunology class, we learned about the hygiene theory as an explanation for why we have autoimmunity. The hygiene theory seems to fit here as well; children who are exposed to a wider variety of microbes will keep their immune system in check by having it target legitimate pathogens as opposed to allergens and self antigens. The part that I wanted to explore was, how do adults that already have hypersensitivities and allergies reduce these symptoms when they get into an environment where they are exposed to a greater variety of microbes? The article cites an animal study in which it is seen that growing on a farm increases regulatory T cell number, which dampens immune response. If the regulatory T cells dampened immune response, wouldn’t individuals that live on a farm be more vulnerable to pathogens because they come across more microbes than individuals who do not live on a farm? Maybe because these individuals are exposed to so many microbes the number of T cells increase to dampen the immune response to keep inflammation in check. I am not sure, but this is very interesting.
This article makes complete sense. Our immune system is basically built and strengthened off exposure. Being born and raised on a farm would benefit ones immune system significantly. This article reminds me of the one where living with a dog reduces allergies. However I think living on a farm would be more advantageous to ones immune system because of the variety of undomesticated animals. This would in turn mean exposure to a myriad of pathogens as compared to only being exposed to domesticated animals such as dogs and cats who have been treated by a vet. When exposed to the pathogen the primary response and production of antibodies would be weak and slow, however whenever exposed to these pathogens again the secondary response will be consist of significantly more antibody production and a faster and stronger response in less time. Ultimately the more exposure to any animal at a younger age the better for an individuals immune system.
This article reminds of the one posted about babies being exposed to dogs and having stronger immune systems essentially. It is all about our relationship and contact with microbes. With the advancement of society is the elimination of important microbes. We are being exposed less, which is making us ultimately weaker when encountering exposure. About a year or 2 back, I took an evolution class and this was a main topic. We have a tradeoff with our relationship with microbes. We could encounter more, and have more frequent sicknesses, but they won’t be as strong or long. Versus, we could experience way less microbes and become ill less frequently, but when we do, it will be very serious or even life threatening. I’m not sure what other think, but I would prefer the first over the latter. We are becoming a society that is afraid of microbes, and is ultimately hurting us. I know this article is specifically regarding allergies, but I think illnesses can factor in as well. It is concerning to think about, because if our immune systems are encountering less microbes, they won’t be prepared to fight, or they may even attack our own antigens. I hope it doesn’t advance this far, but I am worried that if we came to encounter so little microbes, our body may begin thinking our own antigens are bad, and attack itself. It may be a stretch, but I think this could result in an increase in autoimmune diseases.
Like many of the other blog posts on Immunity Tales, I seem to be getting a consistent message… The dirtier you are as a child, the healthier you will be as an adult! But in all seriousness, is this not true? You grow up on a farm, you have a dog, you play with other children, and the list goes on. With every new encounter, you are building up your defenses because you are confronting new microbial organisms, allowing your immune system to develop recognition and a defense system for future encounters. It’s ingenious, really. What doesn’t kill you makes you stronger, and that is ever so evident here. Other messages seem to contribute here as well. Not all microbial organisms are bad! Your body needs some, and many are gained, utilized, and maintained through childhood experiences. I, too, attribute my fairly decent immune system for having no allergies and very few illnesses throughout the year. If you just allow your children to be apart of the world rather than fear it, they will become healthier, happier adults with superb immune systems!
From an evolutionary standpoint it would make sense that we are better adapted to rural conditions over urban environments. I am very curious as to the mechanism behind this. As many have already stated it could be due to the “new allergens” found in cities. But have we considered the opposite; could it be that the immune response is under stimulated in urban settings? Under stimulation could then lead to over reaction when exposed to allergens. An individual raised in a rural setting would constantly be exposed to allergens and so, again from an evolutionary standpoint, it would be reasonable that our immune system has adapted priorities. If you are constantly exposed to an allergen, but do not suffer adverse effects; then why would the immune system bother to respond when exposed to other foreign bodies that pose greater risk? This holds true in my own personal experience. I grew up in small rural towns (I never lived on a farm though). Valdosta, Ga was the biggest “city” I lived in before moving to Atlanta. I used to be outside all the time, at one point I even walked through a small patch of woods to get to school. I never suffered from allergies, that is until I lived here.
Having lived in both types of environments, it has become very clear how drastically different these environments are. Now I live in an apartment inside the perimeter and the closest I get to nature on a daily basis is landscaping architecture. What we don’t realize is just how fabricated even city parks are. Virtually all landscaping in the city is conducted by a company, and these companies purchase mainly purchase their products from industrial farms. What this means is that these plants aren’t even wild plants, they are predominately modified, or at the least homogenous. The end effect is that it drastically reduces the biodiversity that we are exposed to in this environment. It is this lack of biodiversity that fails to keep our immune system stimulated, resulting in over reaction to the few natural stimuli to which we are exposed.
What this really should make us think about is how can we enhance urban environments to better incorporate nature. Here in Atlanta there are a few of these efforts, however they are easily overlooked and are not great enough in number to provide access to the majority of the city’s inhabitants. Such examples are the handful of nature preserves. I haven’t done an exact count and I may be missing some, but I don’t think there are more than half a dozen, and even these are small and losing the battle to urban development and degradation such as runoff pollution. There are also allegedly community gardens, but again they are few in number and hard to find. Personally what I think we should take from research like this is that we need to make greater efforts to maintain our symbiotic relationship with the environment which we have greatly distorted in the last century.