Ribwort Plantain
Summary
Ribwort plantain also identified as Plantago lanceolate is a very important species from the Plantaginaceae family. It is a perennial weed with high ecological plasticity. It grows abundantly mainly in regions such as humid meadows and beside roadsides. Plantain is one of the key reasons for pollinosis in temperate regions. Pla l 1 and Pla l 2 are the two registered allergens till date. Pla l 1 is primarily an indicative marker allergen responsible for the diagnosis of plantain pollen sensitization with high specificity. Pla l 2 is a profilin protein with a molecular weight of 12-15 kDa. It is a small actin-binding protein and is responsible for polysensitization. Plantain allergy is mainly responsible for seasonal allergic rhinitis, rhino-conjunctivitis and in some cases also asthma. Plantain allergen also shows cross-reactivity with pollens like grass, birch, ash, or olive pollen.
Epidemiology
Worldwide distribution
A large population study was conducted in Germany for over 20 years with skin prick testing (SPT) for 6220 individuals to evaluate sensitizations towards weed pollen aeroallergen. The patients were suspected of allergic rhinoconjunctivitis. 26.6% of patients from 1998 to 2007, showed positive results on SPT for plantain. Between 2008 and 2017 this percentage increased to 50.5%.
A Japanese study was conducted on 160 individuals suffering from allergic rhinitis. Among these 141 patients were tested with RAST and 12.8% of these showed positive results to plantain.
A study in China analyzing aeroallergen sensitization in individuals (n=480) suffering from allergic rhinitis showed 29.8% of these patients reported positive to skin prick test for plantain.
In one study conducted in a city Porto of Portugal to check the sensitization of plantain in patients with respiratory allergy, the result showed that 31 percent of the patients showed sensitization for plantain pollen. Plantain was responsible for about 3 percent of the yearly pollen load in the air of Porto. Plantain was found to be the ninth most common pollen in the air of Porto.
Risk factors
A study conducted in the UK found that 28% of patients (n=82) with a history of seasonal respiratory allergy tested positive for skin prick test for plantain pollen extract. The study has also shown when a patient’s sera with seasonal respiratory allergies were subjected to RAST testing with plantain pollen 34%showed positive results.
Sensitization to pollen allergens varies between different regions of the world and is closely related to climatic conditions, degree of urbanization, and plant distribution. In the Mediterranean countries or those with such climate, airborne plantain pollen, along with grass pollen, olive pollen, cypress pollen, plane tree pollen, dust mites, is considered as one of the most common triggers of respiratory allergy.
Pediatric issues
A study was done on a Pacific island in the pediatric population who had wheezing bronchitis. The bronchitis episodes commonly occurred in children less than 4 years of age. The results of the skin test and the serologic test showed that hypersensitivity reaction to plantain allergens was related to bronchitis episodes.
Route Of Exposure
Main
Plantain pollen is generally considered a causative allergen for airborne allergy in Europe.
Clinical Relevance
Allergic rhinitis
Plantain is responsible for about 20 to 30 percent of all the episodes of seasonal allergic rhinitis in the western population. A study was conducted in Japan in about 160 patients with allergic rhinitis to find out the prevalence of plantain pollinosis. The results showed a plantain RAST-positive rate of 12.8 percentage.
Asthma
A study was conducted with 866 patients suffering from allergic rhinoconjunctivitis (ARC) and asthma using skin prick tests to evaluate seasonal allergy. Among these 38.79% were suffering from asthma and ARC. The study reported 45.7% showed positive skin prick test results towards plantain pollen allergen.
Prevention And Therapy
Prevention strategies
Avoidance
It is generally difficult to avoid pollens on daily bases. Some measures that can be taken are to wear, sunglasses and mask. Keep windows of an allergic individual’s house (especially if situated in a tall building) and in a moving car shut. One can also try to avoid walking over open grassy areas, especially during high pollen count.
Cross-Reactivity
Patients with a true monosensitization to plantain are rarely found. The vast majority of the plantain pollen-sensitized patients show concomitant sensitizations and allergies to other pollen allergen sources, such as grass, birch, ash, or olive pollen. Recent studies showed a lack of IgE cross-reactivity of Pla l 1 with homologous allergens. However, plantain pollen also contains the panallergens such as profilin and polcalcin which are present in other pollen sources.
References
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