Major pollen allergen Phl p 5 (Phl p 5) (Phl p 5)

Major pollen allergen Phl p 5 (Phl p 5) is a highly immunogenic protein found in the pollen of Timothy grass (Phleum pratense), serving as a primary trigger for seasonal allergic rhinitis and asthma [UniProt: P43213]. It is classified as a major allergen because more than 50% of grass pollen-allergic individuals exhibit IgE reactivity to it, often showing high-affinity binding that leads to potent mast cell degranulation [WHO/IUIS Allergen Nomenclature]. In clinical practice, Phl p 5 is a central component of allergen-specific immunotherapy (AIT), where it is administered to patients to induce peripheral T-cell tolerance and stimulate the production of protective IgG4 antibodies [PMID: 29104787]. Standardized extracts and recombinant forms of Phl p 5 are used in diagnostic tests and therapeutic vaccines like Grazax and Oralair [FDA Label]. Structurally, Phl p 5 exists in multiple isoforms, such as Phl p 5.0101 and Phl p 5.0201, which share high sequence identity but differ in their T-cell epitope profiles [UniProt: P43213]. The primary therapeutic challenge associated with Phl p 5 is the risk of inducing systemic allergic reactions or anaphylaxis during the desensitization process, requiring careful dose escalation and medical supervision [PMID: 25699545].

Other names

Phl p VTimothy grass pollen allergen 5Phleum pratense allergen 5Major pollen allergen Phl p 5.0101

Allergen-specific immunotherapy (AIT) induces peripheral T-cell tolerance, increases regulatory T-cells (Tregs), and promotes the production of allergen-specific IgG4 antibodies that compete with IgE for allergen binding, thereby inhibiting mast cell and basophil degranulation.