Phleum pratense pollen extract (Timothy grass pollen extract)

Phleum pratense pollen extract is a complex biological mixture derived from Timothy grass, containing several major and minor allergenic proteins such as Phl p 1, Phl p 2, and Phl p 5 (DrugBank, 2024). It is primarily utilized as the active component in allergen immunotherapy (AIT) for the treatment of seasonal allergic rhinitis and conjunctivitis (FDA, 2014). Rather than being a single molecular target, it acts as a therapeutic agent that modulates the patient's immune system to induce long-term tolerance (PubMed, 2021). The mechanism involves the induction of regulatory T cells (Tregs), a shift from Th2 to Th1 cytokine profiles, and the production of allergen-specific IgG4 antibodies that block IgE-mediated mast cell degranulation (StatPearls, 2023). Clinical use is associated with a reduction in allergic symptoms and a decreased reliance on symptomatic medications like antihistamines (NIH, 2022). However, administration carries a risk of systemic allergic reactions, including anaphylaxis, requiring careful patient monitoring and often a boxed warning on pharmaceutical labels (FDA, 2014).

Other names

Timothy grass pollen extractPhl p extractTimothy grass allergen extractPhleum pratense allergen

Induces immune tolerance by shifting the immune response from a Th2-mediated allergic profile to a Th1/Treg-mediated profile, increasing allergen-specific IgG4 blocking antibodies, and reducing mast cell and basophil activation.