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Ribwort Plantain

w234 Pla l 1

Allergen Component
Biological Function pollen tube development
Code w234
IUIS Code Pla l 1
Allergome Code 574
Source Material recombinant, CCD-free protein
Latin Name Plantago lanceolata
Other Names Plantago lanceolata major allergen
Categories Weed Pollens
Molecular Weight 18kDa


Pla l 1 is a major allergen of and marker of genuine sensitization to English plantain (Plantago lanceolata) pollen. Pla l 1 is a member of the Ole e 1-like pollen protein family but displays limited, clinically non relevant, cross-reactivity with other members of this family, most notably with Ole e 1 from olive pollen and Che a 1 from goosefoot pollen.


Worldwide distribution

Plantago lanceolata is a frequent and increasing cause of weed pollinosis under temperate climate worldwide  [1, 2].

Pla l 1 sensitization was initially observed in 86% of P. lanceolata-allergic patients [1]. Subsequent studies reported variable levels, from 92% [3] to 33% - 34% [4, 5] in patients with evocative symptoms and P. lanceolata whole allergen extract sensitization, depending on the methodology of subject inclusion, the geographical area, the relative frequency of pollen multisensitization and the contribution of other plantain allergens [2-5].

This variation is also seen in epidemiological studies addressing subjects referred with a suspicion of allergy, which report locally relevant values of Pla l 1 sensitization, ranging from 0.3 to 7% in Germany [6] and up to 9.6% of pollen-sensitized subjects in the Czech Republic [7].

Environmental Characteristics

Source and tissue

Pla l 1 was identified as the dominant major allergen of P. lanceolata pollen [1].

Pla l 1 is present in P. lanceolata pollen, but not in other tissues, localized mainly in the cytoplasm of the vegetative cell [8]. Levels and temporal peaks of airborne Pla l 1 were reportedly ill-correlated with those of Plantago pollen counts, suggesting the contribution of additional sources of Pla l 1 [9]. 

Risk factors

The main risk factor for developing sensitization to Pla l 1 is exposure to P. lanceolata pollen [10]. Genetic susceptibility might also be involved, as a significant association was reported between Pla l 1 sensitization and the presence of the HLA class II allele DPB1*04:02 in a French adult cohort [11].

Clinical Relevance

Detailed information regarding P. lanceolata pollinosis, which manifests itself mainly as allergic rhinitis, rhinoconjunctivitis and asthma, is available in the whole allergen section. 

Disease severity and prediction

In patients with a case history evocative of P. lanceolata pollinosis and sensitization to P. lanceolata whole allergen extract, the demonstration of Pla l 1 IgE confirms genuine sensitization to this pollen, thus assisting with correct classification of multisensitized patients  [5, 10, 12]. .

Cross-reactive molecules

Pla l 1 exhibits limited and clinically irrelevant cross-reactivity with the major olive pollen allergen Ole e 1 and with Ole e 1-like allergens such as Phl p 11 from Phleum pratense, Che a 1 from Chenopodium album and Sal k 5 from Salsola kali [10, 13].

Molecular Aspects


Pla l 1 is a polymorphic allergen belonging to a large protein family known as Ole e 1-like, broadly expressed in tree, weed, and grass pollen and sharing a beta-barrel fold with a potential ligand binding function [14, 15]. Pla l 1 is thermostable, with its conformation stabilized by the typical Ole e 1-like three intramolecular disulphide bridges and is N-glycosylated in its native form [14, 16]. Pla l 1 carries the major allergenic activity of P. lanceolata whole allergen extract, inhibiting 80% of its IgE-binding, and may form dimers under some conditions [1]. Its proposed biochemical function as a trypsin inhibitor has not been confirmed, especially as trypsin exposure rapidly denaturated Pla l 1 [15]. At the biological level, Ole e 1-like proteins are involved in pollen fertilization, i.e. pre-germination events controlling pollen tube development [17].

Isoforms, epitopes, antibodies

As of January 8, 2022, three isoallergens of Pla l 1 have been included in the World Health Organization (WHO) and International Union of Immunological Societies (IUIS) Allergen Nomenclature [18]. 

Cross-reactivity due to structural similarity

Pla l 1 shares limited sequence identity with other allergenic members of the Ole e 1-like pollen protein family, without clinically relevant cross-reactivity: 27% with Che a 1, the major allergen of the weed Chenopodium album [13], 26% with Sal k 5 from Salsola kali [14] and 38%-42% with Ole e 1 from Olea europaea pollen [16]. 

Diagnostic Relevance

Marker allergen for sensitization to P. lanceolata pollen

Pla l 1 sensitization confirms genuine sensitization to P. lanceolata pollen and is found in 33-92% of patients with P. lanceolata pollinosis, depending on the study population, the geographic area and local pollen exposure [3, 5, 10, 12]. In areas of concomitant sensitization to grass and other weed pollen and overlapping pollination seasons, Pla l 1 assists with the identification of the primary sensitizer [10]. 


Pla l 1 does not cross-react with Ole e 1 and Ole e 1-like allergens from other pollens (olive, grass, weeds) [10]. Importantly, even in patients exhibiting IgE to Ole e 1 and other Ole e 1-like allergens, IgE inhibition experiments confirmed true co-sensitization to Pla l 1 and the absence of cross-reactivity [15]. Therefore, Ole e 1 should not be used as a surrogate marker for sensitization to Pla l 1 [10].


The main route of exposure is through inhalation of P. lanceolata pollen [10]. 

Compiled By

Author: Joana Vitte

Reviewer: Dr. Christian  Fischer


Last reviewed:February 2022

  1. Calabozo, B., D. Barber, and F. Polo, Purification and characterization of the main allergen of Plantago lanceolata pollen, Pla l 1. Clin Exp Allergy, 2001. 31(2): p. 322-30.
  2. Forkel, S., et al., Allergic Rhinitis to Weed Pollen in Germany: Dominance by Plantain, Rising Prevalence, and Polysensitization Rates over 20 Years. Int Arch Allergy Immunol, 2020. 181(2): p. 128-135.
  3. Gadermaier, G., et al., Plantago lanceolata: an important trigger of summer pollinosis with limited IgE cross-reactivity. J Allergy Clin Immunol, 2014. 134(2): p. 472-5.
  4. San Nicolo, M., et al., Relevance of Major Allergens in Weed Pollen Allergy. Int Arch Allergy Immunol, 2021. 182(7): p. 637-641.
  5. Stemeseder, T., et al., Do Plantago lanceolata Skin Prick Test-Positive Patients Display IgE to Genuine Plantain Pollen Allergens? Investigation of Pollen Allergic Patients from the North-East of France. Int Arch Allergy Immunol, 2018. 177(2): p. 97-106.
  6. Hoflich, C., et al., Management of patients with seasonal allergic rhinitis: Diagnostic consideration of sensitization to non-frequent pollen allergens. Clin Transl Allergy, 2021. 11(8): p. e12058.
  7. Panzner, P., et al., A comprehensive analysis of middle-European molecular sensitization profiles to pollen allergens. Int Arch Allergy Immunol, 2014. 164(1): p. 74-82.
  8. Castro, A.J., et al., Pla 1 1 and Ole e 1 pollen allergens share common epitopes and similar ultrastructural localization. J Investig Allergol Clin Immunol, 2007. 17 Suppl 1: p. 41-7.
  9. Gonzalez Parrado, Z., et al., Molecular aerobiology - Plantago allergen Pla l 1 in the atmosphere. Ann Agric Environ Med, 2014. 21(2): p. 282-9.
  10. Matricardi, P.M., et al., EAACI Molecular Allergology User's Guide. Pediatr Allergy Immunol, 2016. 27 Suppl 23: p. 1-250.
  11. Gheerbrant, H., et al., Associations between specific IgE sensitization to 26 respiratory allergen molecules and HLA class II alleles in the EGEA cohort. Allergy, 2021. 76(8): p. 2575-2586.
  12. Til-Perez, G., et al., Sensitization profile in patients with respiratory allergic diseases: differences between conventional and molecular diagnosis (a cross-sectional study). Clin Mol Allergy, 2019. 17: p. 8.
  13. Barderas, R., et al., Identification and characterization of Che a 1 allergen from Chenopodium album pollen. Int Arch Allergy Immunol, 2002. 127(1): p. 47-54.
  14. Castro, L., et al., Sal k 5, a member of the widespread Ole e 1-like protein family, is a new allergen of Russian thistle (Salsola kali) pollen. Int Arch Allergy Immunol, 2014. 163(2): p. 142-53.
  15. Stemeseder, T., et al., Crystal structure of Pla l 1 reveals both structural similarity and allergenic divergence within the Ole e 1-like protein family. J Allergy Clin Immunol, 2017. 140(1): p. 277-280.
  16. Calabozo, B., et al., Cloning and expression of biologically active Plantago lanceolata pollen allergen Pla l 1 in the yeast Pichia pastoris. Biochem J, 2003. 372(Pt 3): p. 889-96.
  17. Fernandez-Gonzalez, M., et al., Secondary Outcomes of the Ole e 1 Proteins Involved in Pollen Tube Development: Impact on Allergies. Front Plant Sci, 2020. 11: p. 974.
  18. IUIS/WHO. IUIS/WHO Plantago lanceolata. 2022  2022 January 13]; Available from: