Timothy grass pollen allergen Phl p 5 (Phl p 5)

Timothy grass pollen allergen Phl p 5 is a major protein allergen derived from Phleum pratense, a significant source of seasonal aeroallergens worldwide. It is classified as a group 5 grass pollen allergen and is recognized by specific IgE antibodies in more than 80% of individuals allergic to grass pollen, making it a critical component for diagnosis and treatment [UniProt Q40960, WHO/IUIS]. Although its precise physiological role in the plant is not fully defined, in humans, it triggers potent IgE-mediated hypersensitivity reactions by cross-linking IgE on mast cells and basophils, resulting in the release of inflammatory mediators [PubMed: 11056501]. In a clinical context, Phl p 5 is a primary target of allergen-specific immunotherapy (AIT). Therapeutic products like Grastek and Grazax use standardized extracts of this allergen to desensitize patients, aiming to modify the underlying disease by inducing T-cell tolerance and increasing protective IgG4 antibodies [StatPearls, FDA]. While effective for long-term symptom reduction in allergic rhinitis and asthma, the administration of Phl p 5 carries a risk of systemic allergic reactions, necessitating careful patient monitoring during the initial phases of therapy [NCBI].

Other names

Phl p VPhleum pratense allergen 5Major pollen allergen Phl p 5Timothy grass allergen 5

Allergen-specific immunotherapy (AIT) involves the repeated administration of the allergen to induce immunological tolerance. This process shifts the immune response from a Th2-dominated profile to a Th1 or regulatory T-cell (Treg) response, leading to the production of blocking antibodies such as IgG4 and IgA which compete with IgE for allergen binding [PMID: 21846871, NIH].