Timothy grass pollen allergen Phl p 1 (Phl p 1)

Timothy grass pollen allergen Phl p 1 is a 27–35 kDa glycoprotein belonging to the beta-expansin family, specifically categorized as a Group 1 grass pollen allergen [UniProt P43213, Thermo Fisher Scientific]. In its native plant environment, it acts as a non-enzymatic cell wall-loosening agent that facilitates fertilization by allowing the pollen tube to penetrate the maternal tissues of the stigma and style [PubMed 10424508, Wikipedia]. In humans, Phl p 1 is the primary initiator of grass pollen allergy, with more than 90% of grass-pollen-allergic individuals exhibiting specific IgE reactivity to this protein [PMC4106562, PMC4607271]. Upon inhalation, Phl p 1 cross-links IgE on the surface of mast cells and basophils, leading to the release of inflammatory mediators and the clinical symptoms of allergic rhinitis and asthma [PubMed 19694723]. This allergen is a critical target for allergen-specific immunotherapy (AIT), where it is administered in standardized extracts or recombinant forms to induce long-term immunological tolerance by shifting the immune response from a Th2 to a Th1 profile [PMC3073371, PMC3166668].

Other names

Pollen allergen Phl p 1Major pollen allergen Phl p 1Beta-expansin-like proteinPhl p IGroup 1 grass pollen allergen

Allergen-specific immunotherapy (AIT) utilizing Phl p 1 induces peripheral immune tolerance by promoting a shift from a Th2-mediated allergic response to a Th1-mediated response. This process involves the induction of regulatory T cells (Tregs) that secrete suppressive cytokines like IL-10 and TGF-beta, and the stimulation of B cells to produce allergen-specific 'blocking antibodies' (IgG4 and IgA). These antibodies compete with IgE for binding to Phl p 1, thereby preventing the degranulation of mast cells and basophils upon subsequent allergen exposure [PMC3073371, PMC3166668, ResearchGate 2025].