Timothy grass pollen allergens (Phl p)

Timothy grass (Phleum pratense) pollen allergens are a group of proteins that serve as the primary triggers for seasonal allergic rhinitis and asthma in sensitized individuals (WHO/IUIS Allergen Nomenclature, 2024). The most clinically relevant components are the major allergens Phl p 1 (a beta-expansin) and Phl p 5 (a ribonuclease-like protein), which are recognized by IgE antibodies in the majority of grass-pollen-allergic patients (PubMed: 10852914). These allergens are the active components in allergen-specific immunotherapy (AIT), such as the sublingual tablets Grastek and Grazax, which are designed to induce immunological tolerance (FDA Label: Grastek, 2014). The therapeutic process involves modulating the T-cell response, increasing the population of regulatory T-cells, and inducing the production of IgG4 blocking antibodies (PubMed: 21545531). By targeting the underlying immune mechanism of the allergic response, these allergens facilitate a long-term reduction in symptoms and decrease the need for rescue medications (StatPearls: Allergen Immunotherapy, 2023). This approach provides a disease-modifying effect that persists even after the cessation of treatment, distinguishing it from symptomatic therapies like antihistamines.

Other names

Phleum pratense pollen allergensTimothy grass allergensPhl p allergensGrass pollen group 1 and 5 allergens

Allergen-specific immunotherapy (AIT) induces immune tolerance by promoting the differentiation of regulatory T-cells (Tregs) and the production of IL-10 and TGF-beta. This leads to a shift from a Th2-dominated response to a Th1-dominated response and the induction of allergen-specific IgG4 "blocking" antibodies that compete with IgE for allergen binding, thereby inhibiting mast cell and basophil degranulation (PubMed: 21545531; StatPearls: Allergen Immunotherapy, 2023).