This still doesn't explain why some people are more allergy-prone than others. "Allergens are everywhere," says Erika von Mutius, an allergy specialist at Munich University Children's Hospital in Germany. "So if this is a defense, why isn't everybody allergic?" According to Medzhitov, allergies may be more common in people with defects in other defensive tactics. For instance, 42 percent of people who have a mutation in a structural skin protein called filaggrin commonly experience allergic skin reactions. "If you don't have optimal physical barriers, you rely on a greater degree on allergic defenses," he says.
And what about the growing body of research suggesting that childhood environment shapes allergy risk? A 2011 study published in The New England Journal of Medicine reported that children who grow up on farms, where they are exposed to many microorganisms, are less likely than other kids to develop asthma and allergies. This idea, known as the hygiene hypothesis, suggests that individuals who encounter a multitude of bacteria and viruses early in life invest more immune resources into type 1 responses at the cost of type 2 reactions, including allergies. Medzhitov maintains that this theory can co-exist with his own. "It's a different aspect of disease susceptibility that has to do with early programming," he says.
Ultimately, Medzhitov's theory raises more questions than it answers, but many agree that the basic tenets are plausible. "It stimulates us as scientists to draw up some new hypotheses," says Kari Nadeau, an immunologist at the Stanford School of Medicine. "The hypotheses need to be tested and might not necessarily be confirmed, but at least this paper drives us to understand allergies better."
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10 Comments
Add CommentThe article states: "allergies involve 'type 2' responses, which are thought to have evolved to protect against large parasites" but gives no indications why it is thought that we did not have them from the beginning.
Reply | Report Abuse | Link to thisWhy does conjecture need to be added. Suggesting that this response “evolved” did not add anything to the understanding of the ideas put forth in the article.
"Large" is a matter of scale. The apparent function of IgE, the immune component most often implicated in allergies, reacts to potential attacks by agents that can't be engulfed by a macrophage. That ain't so big.
Reply | Report Abuse | Link to thisnot-evolved:
Reply | Report Abuse | Link to thisYou seem to be trolling the S.A. forums looking for the key words 'evolved' or 'evolution', and when you find these words you make a silly post that makes no sense. The S.A. boards are devoted to the discussions of SCIENCE, not mythology. Go back to your Flat Earth Society meetings and your Creationism meetings and stop wasting our time.
As a subscriber and online reader, and as a student of science, I would like to see references cited, and for papers and books mentioned in your articles (particularly when they are incompletely mentioned in passing), if used. The three papers mentioned in the fourth paragraph is a great example. There is enough information to get one started if they want to try to locate these papers, but it would certainly would promote further research on the topic if they had clearcut references to go directly to--particularly with readers that don't just settle with what they're told from news sources. It took me about 10-15 minutes to find Medzhitov's (et al.) recent paper after using a few different techniques. I probably could have spent a half hour if I wanted to locate them all to read later.
Reply | Report Abuse | Link to thisI know SA isn't a scholarly journal, nor am I looking for it to be as thorough and void of colorful writing, but a few references at the end of articles would be a nice touch. There are the further reading suggestions at times, but don't often contain some of the works referenced in the article itself. In an age of settling on one generalized news source, we sure could use promotion of visually noticeable references for the content. Thanks.
Due to the limitation of characters that this forum imposes, it dictates that I must submit my Comment in several posts. Commencing with Part 1:
Reply | Report Abuse | Link to thisPart 1.
An allergic reaction is an overactive immune response to an otherwise non-pathogenic (doesn't normally cause illness)stimulus - not a"misdirected immune reaction", as you stated. It is an"overactive"or"hypersensitive" response to something(called an allergen)to which an individual is allergic or hypersensitive.The allergen can be food, medication, animal dander, an insect
sting, the waste matter from dust mites; etc.
The hypersensitivity reaction that most people are familiar with, and refer to as having "allergies",is mediated by a substance called "Histamine"(hence, the medicine for treatment of some allergies called an "Anti-histamine".)
Your statements that "...allergies may actually have evolved to protect us"; followed by:"Runny noses, coughs and itchy rashes keep toxic chemicals out of our bodies ..." are completely erroneous. The runny nose and rash that are symptoms of an individual's allergic reaction to something, are not present
to serve the purpose of "keeping toxic chemicals out of our bodies". Nor has an individual's allergic reaction evolved to protect them.Conversely, it is
literally the subsequent exposure after the first one, that can be far worse to one who is acutely allergic.
You demonstrate complete inaccuracy in the paragraph that begins with the sentence:"Most immunologists consider allergies to be misdirected immune reactions to innocuous substances .... " Your premise that "viral & bacterial infections invoke type 1 immune responses, and allergies involve type 2 responses that have evolved to protect against large parasites"; is completely invalid.I've got news for you - there are not just two "types" of reactions - there are currently four - with some in our field of endeavor favouring a classification system of seven. Regardless of whether there are two, four, or seven - the classification of "Type I" reactions have absolutely nothing to do with "viral & bacterial infections invoking" them - the fact that you would make such a blatant mistake regarding data of this nature is appalling. I am beside myself in an attempt to assimilate any sort of understanding as to how an error of this magnitude could possibly have been made in a publication that calls itself "Scientific American."
You also stated in your article that "allergies are helpful".
(Continued - Part 2.)
Part 2.
Reply | Report Abuse | Link to thisIt escapes me where you got the notion that any allergy has the propensity to be "helpful" - that statement is ridiculously invalid.
Since the content, as well as the premise for your entire article is glaringly incorrect, let me clarify some things for you regarding allergies and allergic reactions:
(I.)Type I reactions(ie, Immediate Hypersensitivity Reactions)involve Immunoglobulin E(IgE)–mediated release of histamine and other mediators from Mast Cells and Basophils.
(II.)Type II reactions(ie, Cytotoxic Hypersensitivity Reactions)involve Immunoglobulin G or Immunoglobulin M antibodies bound to cell surface antigens, with subsequent complement fixation.
(III.)Type III reactions(ie, Immune-Complex Reactions) involve circulating antigen-antibody immune complexes that deposit in postcapillary venules, with subsequent complement fixation.
(IV.)Type IV reactions(ie, Delayed Hypersensitivity Reactions,Cell-Mediated Immunity) are mediated by T cells rather than by antibodies.
Some in our field believe the classification system may be too general,and favour a more recent system of
classification proposed by Sell.[1] This system accounts for the fact that multiple components of the
immune system can be involved in various types of hypersensitivity reactions; and it divides Immuno-
pathologic responses into the following categories:
Inactivation/Activation Antibody reactions
Cytotoxic or Cytolytic Antibody reactions
Immune-Complex reactions
Allergic reactions
T-cell Cytotoxic reactions
Delayed Hypersensitivity reactions
Granulomatous reactions
[1] Sell,S.; Rich,R.R.; Fleisher,T.A.; et al,eds. "Clinical Immunology:Principles and Practice". ed.St. Louis, Mo: Mosby-Year Book
"Allergic reactions manifest clinically as Anaphylaxis, Allergic Asthma, Urticaria, Angioedema, Allergic Rhinitis, some types of drug reactions,and Atopic Dermatitis.These reactions tend to be mediated by IgE,which differentiates them from Anaphylactoid reactions that involve IgE-independent Mast Cell and Basophil degranulation." [2]
[2]Lawlor,G.J.;Fischer,T.J.;Adelman,D.C. - eds. "Manual of Allergy and Immunology"3rd ed Phila.,PA: Lippincott-Raven
"Patients prone to IgE-mediated allergic reactions are said to be 'Atopic'. Atopy is the genetic pre- disposition to make IgE antibodies in response to allergen exposure."[3]
[3] Nimmagadda S.R.;Evans, R. 3rd."Allergy: Etiology and Epidemiology."
(Continued - Part 3)
Part 3.
Reply | Report Abuse | Link to thisNow then, Ms. Moyer - it is abundantly clear that you are not in compliance with the principles and standards of practice of the Society of Professional Journalists; as professional integrity is the corner-
stone of a Journalist's credibility. Journalists should seek the truth and report it - it is the duty of their profession to test the accuracy of information from all sources; and exercise great care to avoid inadvertent error. Deliberate distortion is NEVER permissible. We are addressing this with you, because this article is so glaringly and ridiculously invalid, that you could not possibly have performed even a modicum of research in obtaining the information. This article unarguably gives rise to the question:
"Just what kind of show are you people running over there now?"
Against our better judgement, we'll give you the benefit of the doubt; and presume that you will certainly be accountable for what you've laid down here; and respond by explaining that you inadvertently got the information in this article mixed up with the information for another article .... and it'd be best if you just left it at that. I mean, really - what else could you say? That you're in Elementary School?
In closing - for you to say nothing; is saying
something.
13 Inches - in all fairness, 'not-evolved' stated a valid inquiry - that you would make mockery of the inquiry is extremely inappropriate. As well, the liberty you take by informing him/her what the Scientific American forums are for; combined with the instruction for him/her to "go away", as it were; insinuates that you think you have the authority to do so. I am of the educated opinion that the comment that
Reply | Report Abuse | Link to this'not-involved' made was not at all silly, and it made complete sense to me. Kindly explain what gives you the right to believe it is acceptable to speak to anyone in such a derisive manner; and just who the he__ do you think you are to speak to anyone in such an authoritative manner; as though you have the right
to, or are in the position to do so?
I found your personal attack of "not-evolved" extremely offensive as well as abusive. I'm here to tell you, tough guy; it really gives pause for one to wonder what motivated you to submit such a post.
Of paramount importance, for you to make the statement that "the S.A. boards are devoted to the discussions of science .." under the umbrella of this ridiculously inaccurate article, is ludicrous; if not outright laughable. What were you thinking?!
Thanks for the update on terminology. Back in the days when I was trying to understand my allergies they always lumped T-cells and B-cells under the label antibodies. It is nice to know that we are more specific now.
Reply | Report Abuse | Link to thisI notice that you dislike the way this article presented things but did not directly address the hypothesis presented by Ruslan Medzhitov. Have you read his work and do you have an opinion on it? Is he simply out of date on terminology or was his work taken out of context?
In regards to the posts by Not-evolved and 13Inches; they are both forum trolls. Not-evolved always seems to take exception to anything that challenges a "magical creation" theory of existence. I have yet to find anything even vaguely resembling evidence that the Earth and all of the universe is only a few thousand years old. There are many such as myself that firmly believe that God created the entire universe via a process that obeys physical laws and required billions of years to reach our current state of existence. For that reason the challenge of the use of the term evolved should have a basis in science rather than superstitious shamanism.
Reply | Report Abuse | Link to thisWe are no longer in the era of burning witches and one would expect somewhat more intelligent debate on the topic posted on a forum where that topic is under discussion. This topic is allergies and not the magical branch of creationism.
As for 13Inches; Most of their posts are noxious but occasionally there is a post that is brilliant. Obviously this is a person that has never had to mature. I hold out hope for this person because many of my earlier posts were little better. As I've gotten older I have moderated my behavior and hopefully am not so abrasive and intolerant. I guess I'm evolving as a person.