title: Responses to ragweed pollen in a pollen challenge chamber versus seasonal exposure identify allergic rhinoconjunctivitis endotypes.
abstract: BACKGROUND
  The level of concordance between allergic symptoms induced on exposure to pollen in a pollen challenge chamber (PCC) versus the natural season is unknown.
  
  
  OBJECTIVE
  We sought to test the hypothesis that the symptom levels of allergic rhinoconjunctivitis elicited after out-of-season exposure to short ragweed in a PCC and during the natural season for giant ragweed pollen are highly correlated.
  
  
  METHODS
  Thirty-one ragweed-sensitive participants recorded symptoms for 15 days during the natural giant ragweed season in San Antonio, Texas. Twenty-six of these participants were challenged to short ragweed pollen in a PCC for 3 hours per day for up to 4 days.
  
  
  RESULTS
  In the PCC participants were dichotomized into those in whom low versus high levels of symptoms developed slowly or rapidly (ie, slow/low vs rapid/high). Each successive exposure visit associated with a progressive increase in symptom levels that approximated those experienced during the natural season. Hierarchic clustering identified 3 endotypes: endotypes I and II reflected concordantly low (n= 7) versus high (n = 14) total symptom scores (TSSs) in both the natural season and the PCC, respectively. Accordingly, the correlation between the TSSs recorded in the natural season and in the PCC for these 21 participants was very high. Although participants with endotype III (n = 5) had greater TSSs in the natural season than in the PCC, the degree of correlation between the TSSs remained high.
  
  
  CONCLUSIONS
  Our findings affirm our hypothesis, underscore the high cross-reactivity between distinct pollens, and highlight the utility of the PCC to identify novel allergy endotypes that might have contrasting mechanistic underpinnings and potentially therapeutic responses.
authors.affiliation: Biogenics Research Chamber, San Antonio, TX 78229, USA. robert.jacobs7025@sbcglobal.net
authors.forename: Robert L
authors.initials: RL
authors.lastname: Jacobs
authors.forename: Nathan
authors.initials: N
authors.lastname: Harper
authors.forename: Weijing
authors.initials: W
authors.lastname: He
authors.forename: Charles P
authors.initials: CP
authors.lastname: Andrews
authors.forename: Cynthia G
authors.initials: CG
authors.lastname: Rather
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Ramirez
authors.forename: Sunil K
authors.initials: SK
authors.lastname: Ahuja
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000485:Allergens / Q000276:immunology; D031164:Ambrosia / Q000276:immunology*; D003233:Conjunctivitis, Allergic / Q000209:etiology / Q000276:immunology / Q000503:physiopathology*; D004781:Environmental Exposure; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011058:Pollen / Q000276:immunology*; D006255:Rhinitis, Allergic, Seasonal / Q000209:etiology / Q000276:immunology / Q000503:physiopathology*; D012621:Seasons; D013781:Texas; D055815:Young Adult
chemical_list: D000485:Allergens