Oat sensitivity: Difference between revisions

'''Oat sensitivity''' represents a sensitivity to the proteins found in [[oat]]s, ''Avena sativa''. Sensitivity to oats can manifest as a result of allergy to oat seed storage proteins either inhaled or ingested. A more complex condition affects individuals who have [[gluten-sensitive enteropathy]] in which there is an [[autoimmune disease|autoimmune response]] to avenin, the glutinous protein in oats similar to the gluten within wheat. Sensitivity to oat foods can also result from their frequent contamination by wheat, barley, or rye particles.<ref name=PenaginiDilillo>{{cite journal | vauthors = Penagini F, Dilillo D, Meneghin F, Mameli C, Fabiano V, Zuccotti GV| title = Gluten-free diet in children: an approach to a nutritionally adequate and balanced diet | journal = Nutrients | volume = 5| issue = 11| pages = 4553–65| date = Nov 18, 2013| pmid = 24253052|pmc= 3847748| doi = 10.3390/nu5114553| doi-access = free }}</ref>

Studies on farmers with grain dust allergy and children with [[atopy]] [[dermatitis]] reveal that oat proteins can act as both respiratory and skin allergens.<ref name=pmid17919139>{{cite journal |vauthors=Boussault P, Léauté-Labrèze C, Saubusse E, etal |title=Oat sensitization in children with atopic dermatitis: prevalence, risks and associated factors |journal=Allergy |volume=62 |issue=11 |pages=1251–6 |date=November 2007 |pmid=17919139 |doi=10.1111/j.1398-9995.2007.01527.x |s2cid=44678077 }}</ref><ref name=pmid16805419>{{cite journal |vauthors=Codreanu F, Morisset M, Cordebar V, Kanny G, Moneret-Vautrin DA |title=Risk of allergy to food proteins in topical medicinal agents and cosmetics |journal=Eur Ann Allergy Clin Immunol |volume=38 |issue=4 |pages=126–30 |date=April 2006 |pmid=16805419 |doi= |url=}}</ref><ref name=pmid12464060>{{cite journal |vauthors=De Paz Arranz S, Pérez Montero A, Remón LZ, Molero MI |title=Allergic contact urticaria to oatmeal |journal=Allergy |volume=57 |issue=12 |pages=1215 |date=December 2002 |pmid=12464060 |doi= 10.1034/j.1398-9995.2002.23893_7.x|urls2cid=33135275 }}</ref><ref name="pmid10871113">{{cite journal |vauthors=Pazzaglia M, Jorizzo M, Parente G, Tosti A |title=Allergic contact dermatitis due to avena extract |journal=Contact Derm. |volume=42 |issue=6 |pages=364 |date=June 2000 |pmid=10871113 |doi= |url=}}</ref><ref name=pmid6154431>{{cite journal |vauthors=Baldo BA, Krilis S, Wrigley CW |title=Hypersensitivity to inhaled flour allergens. Comparison between cereals |journal=Allergy |volume=35 |issue=1 |pages=45–56 |date=January 1980 |pmid=6154431 |doi= 10.1111/j.1398-9995.1980.tb01716.x|urls2cid=10966071 }}</ref> Oat dust sensitivity in farms found 53% showed reactivity to dust, second only to barley (70%), and almost double that of wheat dust.<ref name="pmid3709486">{{cite journal |vauthors=Manfreda J, Holford-Strevens V, Cheang M, Warren CP |title=Acute symptoms following exposure to grain dust in farming |journal=Environ. Health Perspect. |volume=66 |issue= |pages=73–80 |date=April 1986 |pmid=3709486 |pmc=1474397 |doi= 10.2307/3430216|jstor=3430216 |publisher=Brogan &#38}}</ref> The 66&nbsp;kDa protein in oats was visualized by 28 out of 33 sera (84%). However, there was evident non-specific binding to this region and thus it may also represent [[lectin]]-like binding.<ref name=pmid8087661>{{cite journal |vauthors=Varjonen E, Savolainen J, Mattila L, Kalimo K |title=IgE-binding components of wheat, rye, barley and oats recognized by immunoblotting analysis with sera from adult atopic dermatitis patients |journal=Clin. Exp. Allergy |volume=24 |issue=5 |pages=481–9 |date=May 1994 |pmid=8087661 |doi= 10.1111/j.1365-2222.1994.tb00938.x|urls2cid=23053287 }}</ref> IgA and IgG responses, meanwhile, like those seen to [[anti-gliadin antibodies]] in celiac disease or dermatitis herpetiformis, are not seen in response to avenins in atopic dermatitis patients.<ref name=pmid8753845>{{cite journal |vauthors=Varjonen E, Kalimo K, Savolainen J, Vainio E |title=IgA and IgG binding components of wheat, rye, barley and oats recognized by immunoblotting analysis with sera from adult atopic dermatitis patients |journal=Int. Arch. Allergy Immunol. |volume=111 |issue=1 |pages=55–63 |date=September 1996 |pmid=8753845 |doi= 10.1159/000237346|url=}}</ref> Food allergies to oats can accompany atopy dermatitis.<ref name=pmid18447144>{{cite journal |vauthors=Estrada-Reyes E, Hernnández-Román MP, Gamboa-Marrufo JD, Valencia-Herrera A, Nava-Ocampo AA |title=Hypereosinophilia, hyper-IgE syndrome, and atopic dermatitis in a toddler with food hypersensitivity |journal=J Investig Allergol Clin Immunol |volume=18 |issue=2 |pages=131–5 |year=2008 |pmid=18447144 |doi= |url=}}</ref> Oat avenins share similarities with γ and ω-gliadins of wheat — based on these similarities they could potentiate both enteropathic response and anaphylactic responses. Oat allergy in gluten-sensitive enteropathy can explain an avenin-sensitive individual with no histological abnormality, no T-cell reaction to avenin, bearing the rarer [[HLA-DQ2#DQ2.2 and coeliac disease|DQ2.5''trans'']] phenotype, and with anaphylactic reaction to avenin.<ref name=pmid15526039>{{cite journal |vauthors=Arentz-Hansen H, Fleckenstein B, Molberg Ø, etal |title=The molecular basis for oat intolerance in patients with celiac disease |journal=PLoS Med. |volume=1 |issue=1 |pages=e1 |date=October 2004 |pmid=15526039 |pmc=523824 |doi=10.1371/journal.pmed.0010001 }}</ref>

Oat toxicity in people with [[gluten-related disorders]] depends on the oat [[cultivar]] consumed because the [[immunoreactivity|immunoreactivities]] of toxic prolamins are different among oat [[cultivar|varieties]].<ref name=PenaginiDilillo /><ref name=CominoMoreno2015 /> Furthermore, oats are frequently cross-contaminated with the other gluten-containing cereals.<ref name=PenaginiDilillo /> Pure oat (labelled as "pure oat" or "gluten-free oat"<ref name=CiacciCiclitira2015>{{cite journal| vauthors=Ciacci C, Ciclitira P, Hadjivassiliou M, Kaukinen K, Ludvigsson JF, McGough N |display-authors=etal| title=The gluten-free diet and its current application in coeliac disease and dermatitis herpetiformis. | journal=United European Gastroenterol J | year= 2015 | volume= 3 | issue= 2 | pages= 121–35 | pmid=25922672 | doi=10.1177/2050640614559263 | pmc=4406897 | type=Review}}</ref>) refers to oats uncontaminated with any of the other gluten-containing cereals.<ref name=CominoMoreno2015>{{cite journal | vauthors = Comino I, Moreno Mde L, Sousa C | title = Role of oats in celiac disease | journal = World J Gastroenterol | volume = 21 | issue = 41 | pages = 11825–31 | date = Nov 7, 2015 | pmid = 26557006 |pmc= 4631980 | doi = 10.3748/wjg.v21.i41.11825 |quote= It is necessary to consider that oats include many varieties, containing various amino acid sequences and showing different immunoreactivities associated with toxic prolamins. As a result, several studies have shown that the immunogenicity of oats varies depending on the cultivar consumed. Thus, it is essential to thoroughly study the variety of oats used in a food ingredient before including it in a gluten-free diet. | doi-access = free }}</ref>

Some cultivars of pure oat could be a safe part of a gluten-free diet, requiring knowledge of the oat variety used in food products for a gluten-free diet.<ref name=CominoMoreno2015 /> Nevertheless, the long-term effects of pure oats consumption are still unclear<ref name=HaboubiTaylor2006>{{cite journal|vauthors=Haboubi NY, Taylor S, Jones S|title=Coeliac disease and oats: a systematic review|journal=Postgrad Med J|volume=82|issue=972|pages=672–8|date=Oct 2006|pmid=17068278|pmc=2653911|doi=10.1136/pgmj.2006.045443|type=Review}}</ref> and further studies identifying the cultivars used are needed before making final recommendations on their inclusion in the gluten-free diet.<ref name=DeSouzaDeschenes2016>{{cite journal| vauthors=de Souza MC, Deschênes ME, Laurencelle S, Godet P, Roy CC, Djilali-Saiah I| title=Pure Oats as Part of the Canadian Gluten-Free Diet in Celiac Disease: The Need to Revisit the Issue. | journal=Can J Gastroenterol Hepatol | year= 2016 | volume= 2016 | issue= | pages= 1–8 | pmid=27446824 | doi=10.1155/2016/1576360 | pmc=4904650 | type= Review | doi-access=free }}</ref>

Within the same study, three other proteins were identified, one of them an α-[[amylase]] inhibitor as identified by protein homology. A follow-up study showed that most celiacs have anti-avenin antibodies (AVAs), with a specificity and sensitivity comparable to [[anti-gliadin antibodies]].<ref name="pmid10964162">{{cite journal |vauthors=Ribes-Koninckx C, Alfonso P, Ortigosa L, etal |title=A beta-turn rich oats peptide as an antigen in an ELISA method for the screening of coeliac disease in a paediatric population |journal=Eur. J. Clin. Invest. |volume=30 |issue=8 |pages=702–8 |date=August 2000 |pmid=10964162 |doi=10.1046/j.1365-2362.2000.00684.x |s2cid=29004147 }}</ref> A subsequent study found that these AVAs did not result from cross-reaction with wheat.<ref name="pmid12889560">{{cite journal |vauthors=Hollén E, Högberg L, Stenhammar L, Fälth-Magnusson K, Magnusson KE |s2cid=218911012 |title=Antibodies to oat prolamines (avenins) in children with coeliac disease |journal=Scand. J. Gastroenterol. |volume=38 |issue=7 |pages=742–6 |date=July 2003 |pmid=12889560 |doi= 10.1080/00365520310003156|url=}}</ref> However, recently it has been found that AVAs drop as soon as [[Triticeae glutens|''Triticeae'' glutens]] are removed from the diet.<ref name="pmid18224563">{{cite journal |vauthors=Guttormsen V, Løvik A, Bye A, Bratlie J, Mørkrid L, Lundin KE |s2cid=3421741 |title=No induction of anti-avenin IgA by oats in adult, diet-treated coeliac disease |journal=Scand. J. Gastroenterol. |volume=43 |issue=2 |pages=161–5 |year=2008 |pmid=18224563 |doi=10.1080/00365520701832822 |url=}}</ref> Anti-avenin antibodies declined in treated celiacs on an oat diet in 136 individuals, suggesting oats can be involved in celiac disease when wheat is present, but are not involved when wheat is removed from the diet. The study, however, did find an increased number of patients with higher intraepithelial [[lymphocytes]] (IELs, a type of white bloodcell) in the oat-eating cohort. Regardless of whether or not this observation is a direct allergic immune response, by itself this is essentially [[benign]].{{citation needed|date=June 2016}}

The overlap of the antibody and T-cell sites, given trypsin digestion of avenin, suggest this region is dominant in immunity. The TCR-site1 was synthetically made as deamidated ("~E~"), and native peptide requires transglutaminase to reach full activation. Two studies to date have looked at the ability of different oat strains to promote various immunochemical aspects of celiac disease. While preliminary, these studies indicate different strains may have different risks for avenin sensitivity.<ref name="pmid17852883">{{cite journal |vauthors=Silano M, Di Benedetto R, Maialetti F, etal |s2cid=38268535 |title=Avenins from different cultivars of oats elicit response by coeliac peripheral lymphocytes |journal=Scand. J. Gastroenterol. |volume=42 |issue=11 |pages=1302–5 |date=November 2007 |pmid=17852883 |doi=10.1080/00365520701420750 |url=}}</ref><ref name="pmid17376046">{{cite journal |vauthors=Silano M, Dessì M, De Vincenzi M, Cornell H |title=In vitro tests indicate that certain varieties of oats may be harmful to patients with coeliac disease |journal=J. Gastroenterol. Hepatol. |volume=22 |issue=4 |pages=528–31 |date=April 2007 |pmid=17376046 |doi=10.1111/j.1440-1746.2006.04512.x |urls2cid=38754601 }}</ref>